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1. This person has already started an extensive discussion about his plans for setting up a two-person rowing boat on another thread, and that discussion included setting up a canoe for two-person rowing. Of course, you already know that because you posted there and said you'd be watching the replies closely. I don't know about you, but I kinda figured that if his supply of spendable cash had suddenly quadrupled so that he could afford a guide-boat he'd be back on his other discussion asking how to find the boat he already said that he REALLY wants.
2. The guide-boats I've seen or heard about are not set up for two people to be rowing at the same time. All guide-boats that I've seen or heard about DO have two rowing stations, but one of these stations is at the center seat, to be used when rowing solo, and the other is at the front seat, which is used when the boat carries two people. Since the rear seat is located at the stern of the boat (just like a canoe), the boat is in proper trim for two people when one of them sits in the front and the other sits in the rear. You can't install a rowing station at the rear seat if it's mounted at its normal location because there would be no room for the rower's legs (sit facing backward in the rear seat of one of your canoes and see how much legroom you have). Therefore, for boats with the normal seating locations, positioning two people at the two available rowing stations will cause the boat to be woefully out of trim. The OP is definitely looking for a boat for two people, with both of them rowing. I imagine it's possible to set up a guide-boat so that both people could row at the same time and the boat would be in trim, but it would need to be custom-built or greatly modified by the user after purchase, since both the front and rear seat mounts would need to be built into the hull at very unorthodox locations. I'm not a racer like you, but I've seen a lot of photographs of guide-boats with two people in races, and in each case they've propelled the boats in the traditional way (front person rowing, rear person paddling).
I just did some looking online, and I DID find couple "guide-boats" set up for doubles rowing, which didn't require any modification since they used drop-in sliding seats. One of them wasn't a guide-boat by any stretch of the imagination, but the other was (it had a square stern though, and I'm not sure how common that was on the originals). There's still that issue of price, and with racing-style oars and sliding seats with outriggers, for a new one the price will be 5.3 times as much as what the OP wants to spend, but MAYBE a used one could be located which the seller will part with for such a small fraction of original cost.
You won't be rowing "doubles" with an Adirondack guide-boat unless it's a very non-traditional model, and preferably a very long one. The ones made by the company you provided the link to are fantastic boats (I've been rowing mine for close to ten years and couldn't be happier with it). However, they are quite traditional in how the seats and rowing stations are placed, so they are great for two people with one rowing and one paddling, but if you put both people at the two available rowing stations you'll need additional ballast, nearly equal to the weight of the bow-station rower, piled into the stern. Total weight in that situation is "do-able" but far beyond what would be a "high-performance" payload. In fact, if both people weigh around 200 pounds, I think adding close to 200 pounds EXTRA just to balance the trim would overload the boat (600 pounds in a 15-foot boat!).
$5185 in carbon. I have lived in the Adirondacks and know what I have seen in guideboats. And never two rowers at the same time. Does that mean you never can have two paddle a guideboat though? NO. I just have never seen it. Probably because you need three people.. One is ballast
This is a wonderful story from Willem Lange one of our areas premier storytellers.
Yes, I tossed that 200-pound figure out as an example, knowing that the original poster wants to put two adult males in the boat. I don't know how much those two adult males will weigh (maybe not that much since I get the impression they are still pretty young), but since I'm a lightweight myself, I tend to notice that the majority of people past their late 30s weigh a third to half again as much as I do, and that very few of them weigh less than 200.
If your wife is 120, I think you'll still find it a bit difficult to get good end-to-end trim when using the two rowing stations. However, with one of you in each end (as the boat is designed for), carrying some gear with you and putting it at her end is bound to result in better trim (as long as you don't weigh more than twice as much as she does). Still, because the stern seat is tucked more tightly into the pointy end of the boat than the bow seat, you'll find it easier to trim the boat when she's in back than when you are in the back.
With one rower at the front and one paddler at the rear, the boat really cruises. Paddling isn't as efficient as rowing, but believe me, as the rower, you can really feel the difference in speed (and how hard or easy it is to pull the oars) between times when the stern person is paddling and when they are not. Sometimes it's nice that the stern person is facing forward to see what's ahead, and to help with the steering too.
I car-top the boat and have no difficulty doing so. This boat is more awkward to swing up onto your shoulders than a canoe since there are no thwarts or "solidly mounted" seats (the center seat is tied in) to grab during the initial part of the lift, but you could always tip one end up while the other end is on the ground and get underneath it that way. My method is to bend down and grab the gunwales at opposite sides of center and simply swing the boat up over my head and onto my shoulders. I usually just put the front edge of the middle seat across my shoulders, but the center seat is pretty close to the floor (you have to tilt the front of the boat up and tilt your head down a bit), so if I had to carry it a really long distance I'd attach a portage yoke. Back when I bought mine, the catalog weight was 65 pounds. I see that they've changed the listed weight to 70 pounds since then, but I don't know if they weigh more now, or if they've redefined the average weight. In any case, to me my guide-boat always "feels" lighter than my Nova Craft Supernova (canoe), which supposedly weighs 58 pounds (I seem to remember verifying this on the scale once too). I have no idea why the heavier of those two boats always feels lighter to carry.
If you have a long vehicle and a short distance between your cross bars, you may have problems with having enough clearance between the gunwales and your car's roof, because of the pronounced end-to-end curvature of the gunwales.
You can pivot the boat as you describe, but I think you'll find you want to put the end of the boat on some kind of pad. The brass plate you speak of is tiny (only big enough to mount a painter ring), so any irregularities on the ground are going to chew up the wood. Also, brass will get chewed up pretty quickly too if you are on any kind of pavement when you do this.
Your cross-bar spread of 46 inches should be enough on a car that size. I don't think you'll have to worry about gunwales hitting the roof.
If you carry the boat solo, you can simply walk up behind your car so that the front of the boat overlaps it, and squat down so that one end of the boat is on your car and the other end is on the ground. Then just pick up the low end and slide it on. I think you can probably get your rear cross bar close enough to the back of the car to make this work, but otherwise you could lay a blanket or something (I used to have a home-built "rear-extending" cross bar used just for loading, until I mounted my rear cross bar a few inches farther back). OR, you could probably get a tall bucket or something on which to rest the back end of the boat for that initial loading position. With the back end a little higher, you'll be able to rest the front end on a cross bar without risk of gunwales contacting the roof. With two people loading the boat, you should have no problem (there are still some tricks you can use to make things easier).
If you guys want to have your wife row from the front while you paddle from the back, trim will be more of an issue. All I can say is try it and see, but the more stuff you bring with you to put at her end of the boat, the better your trim will be. I haven't used the boat all that much when out-of-trim due to differing weights of the occupants, but I've done it enough to know that having perfect trim usually isn't essential.
I'm sure you could use a double-bladed paddle, but I see no reason to. But then, I love single-blade paddles and technique. Anyway, you can apply stronger effort close alongside the hull with a single than with a double, and you won't get all that water dripping into the boat. Also, if you can synchronize the paddler's strokes with those of the rower, that's a better way to go, and it's much easier to synchronize a single-blade paddle with the oars (you could synchronize every other stroke with a double-blade, but I think the cadence would be less natural).
If the rear person is single-blade paddling, it will help if the paddler knows how to paddle a canoe from the stern and apply a bit of correction to every stroke, but if not, the rower can apply that correction with the oars. The rower should learn to paddle equally well with either hand crossed in front of the other. The hand that starts out with the longer reach can very easily and naturally apply a bit of turning force to the boat, so being able to put either hand as the farther-reaching one means you can counteract the paddling of your partner no matter which side they are paddling on.