60" extension on 22" spread
This is what I’ve been using for the past 2+ years:
http://www.pbase.com/kocho/image/106907342.jpg
and
http://www.pbase.com/kocho/image/117401917.jpg
Works great. The Mako saddles fit roughtly under the bulkheads of most kayaks (regardless of length). The forces from the front/rear tide down ropes are not that big and with some flex built-in my wood-board extension, the saddles, and the ropes, these forces act quite gently on the kayak while still preventing excessive swinging in any direction. I like the slight flex I get - it is like a shock absorber for my kayak -
The saddles stick firmly to the hull so there is no rubbing - all flexing is elsewhere and does not cause stress to the hull. Anyway, hulls can take a lot more than a little road bump on such setup. Of course, the tie-downs are just barely tight, not ratcheted-down.
Nice job
Glenn explained things very well above, I’m in complete agreement with his conclusions. Plus, Kocho raises an important point. The long bars (8 and 9 feet long on mine) definitely act as shock absorbers, allowing the boat to move up and down with no sharp shocks, and very little stress. This is not necessarily obvious, but it’s very clear in use, and prevents excessive stresses and flex in the hull.
yes, nice job
I believe the dude with the 21’ row boats, on the mini in the picture on the link I posted, tied the ends of the cradles down to the bumpers. Kocho, I’m impressed and envy your gas mileage.
In response
"Now, for a bit of critical thinking - what happens when the cross bars are very close together (think about torque and forces, they will act on both the boat and your car). How will those forces change if mount points on your car remain as before while you implement cradle extenders for your boat?
It might be a little hard to visualize all the twisting and shouting, just for experimentation bring those cross bars on your rack to 22 inches, try to twist your kayak and observe.
Oh, didn’t you say that you were not totally happy with wind a windy day with 17 footer on your wagon?"
You have pretty much echoed my thoughts on the subject. I’ve been thinking of going to cradles that would carry the the kayak flat, rather on its side, to minimize cross wind stresses. One day coming back from Lake Erie I took slower back roads as that day the winds were gusting to over 50 mph and I wasn’t enjoying it at all. Hopefully a flat boat would be less subject to lateral stress associated with cross winds.
As mentioned below, a SlipStream style carrier would lower vertical stresses as well. In all, kicking this stuff around here really helps.
Racks for rowing shells
These can be used for long kayaks, too.
http://www.rathburn.net/rowing/article/Car_Top_Shell/Car_Top_Shell.html
http://www.adirondackrowing.com/economy_shell_rack.htm
race boats
You see these things all the time with racing kayaks, rowing shells used for racing etc. These guys/gals wouldn’t be using them if they didn’t work, these boats are fragile and fairly pricy.
Bill H.
Horizontal Saddles
If you're going with the close spread an alternative cradle system I've become a fan of are Marco Kayak Saddles. Provides about a foot of carpeted contact area with the hull and $120 (skinny bars)-$135/pair(factory aero bars).
Just another option as long as you're threshing out possibilities.
See you on the water,
Marshall
The River Connection, Inc
Hyde Park, NY
www.the-river-connection.com
Going with the 887s
Audi has done a nice job with the cross bar system. Even though the spread is short, the bars are very well secured in the door frames. I would classify the mounting arrangement as “semi-permanent” as it’s not easy putting 'em on or taking 'em off.
I’m dumping the j-cradles and will go with the SlipStream system as it looks easy to mount and unmount. And even if I wasn’t switching cars, I’d probably still go for a hull down transport system to reduce windage issues. There have been several times when I’ve felt the wind trying to shove my kayak off the car. And doesn’t the force square with the velocity?.. I hate it when exponential forces are working against me 
love it
If it fits the 22 inch span you’ll love the Slipstream. Got one last year for my little Subaru and it’s awesome. Slide my boats right off the back like butter which cause I’m at just 5 ft tall had been a real problem in past years with other cradles. Say YES to bow and stern straps even though your cradle spacing with the Slipstream is going to be much wider than 22 in.
I have a Tempest 170
that I carry on my '86 El Camino. The spread of the bars is about 20". I know the manufacturers do not recommend this small a distance between the bars, but I have never had an issue transporting my boat as long as I use the bow and stern lines. I would never think of transporting it without those lines in place.
Yeah, I hear you…
…I’m 5’6" and my A4 Avant with its sport suspension has a low roof but with the J cradles I still have to reach for the sky to get my kayak up there. This can be a ‘problem’ on windy days.
And I promise to keep using bow and stern ties… wouldn’t drive across the block without 'em.
They look nice but…
…I’m going with the Thule 887xt’s as they should be easier to put on and take off plus the cradles curve around the hull nicely. Additionally I can load the kayak via the rear roller, not that hefting it overhead would be an issue with a very low roof line.
I’m picking up the new ride in the latter half of February. Audi is maybe the only car manufacturer that has taken the trouble to design cross bars specifically for their sports car. It will be interesting to see how it works for a kayak transporter )
Just out of curiosity…
What kind of "small two seater sports car" has a roof rack?
None of these have them:
http://www.google.com/images?um=1&hl=en&biw=1280&bih=909&tbs=isch:1&sa=1&q=sports+cars+2+seat&aq=f&aqi=&aql=&oq=
Never heard of such an animal?
Paddle easy,
Coffee
I’m picking up…
an Audi TT-S. Audi makes (well, actually Thule) a set of cross bars specifically for the TT series. There’s a rubber gasket along the top of the door frame. When you pull it back you can find front and rear slots with internal pins that lock onto the cross bar support mounts.
This setup allows the bars to lock into the door frame with minimal roof contact. It looks like a pretty solid base system.
Audi’s bars retail for around $370 but I mananged to snag a set for $94.
Anyhow I think that when coupled with the Thule 887xt’s I’ll have a decent setup. And naturally I secure the bow and stern.
While the TT-S isn’t large, it still manages to have plenty of room for carrying gear. It also gets nice gas mileage and will be a rocket after I have the ECU remapped for 322 hp
FRIGGIN’ SWEET!!!
Paddle easy,
Coffee
Your bio…
…suggests a guy who likes his baby wipes I really hate those camping trips where you are expected to pack out your used TP.
A few years ago I rafted down the Tatsheshini/Alsek river with a guided group. I was shocked… shocked… to be told that we had to pack out EVERY THING. Took me back to my childhood, shoveling out the barn basement after 200 head of sheep spent the winter indoors without flushing.