location of D-rings
do you put your front D-ring rectangle fore or aft of the front thwart? I usually put my pack aft and still have room to kneel, but was wondering if I should move it fore. Although it’s probably better to center your cargo.
I would think the back D-ring rectangle must be aft of the back thwart.
location of D-rings
2 sets of 4 = 2 pack locations
There are two sets of four anchors for tying down packs (or whatever other gear). I just looked at my boats to refresh my memory on thwart locations, etc.
One set is right behind the seat, and there's a thwart a short distance behind the seat, so that means a pack placed there sits beneath the thwart (which actually makes holding it in place even easier). If the pack were to be set upright (and would thus need to be placed right behind the thwart instead of under it), one could still use the tie-downs as is to secure it there, because when the pack sits upright it occupies less floor space and would still be within the area of the tie-downs. Some solo canoes have the thwart *right* behind the seat, so whether or not there's room for the whole pack beneath the thwart wouldn't ever be an issue on such boats.
The second set is located so that it will anchor a pack that's placed just in front of where my knees go. There's a thwart at the forward edge of a pack placed at that location.
I put the main pack right behind the seat, as that's closest to center. A heavy pack placed there DOES affect trim, even if not as much as putting it at any other location would do. That's why I always use two packs. The lighter pack goes in the forward location, which is farther away from the center of the boat than the rear pack location. Remember the teeter-totter principle, that two unequal weights will balance out if the heavier one is closer to center than the lighter one. If I figure the lighter pack is "too light" to achieve this affect, I'll put other things more forward of center too, things like my drinking-water supply. If the front pack is a little heavier than it needs to be, the water supply (or whatever else) gets shifted rearward. If I think the balance is pretty good, the water bag goes right between my knees or even a little under the seat.
I don't fret over trim as much as this might make it seem. I just 'eyeball' my gear, knowing the approximate relative weights of the two packs, and make a common-sense adjustment as far as where to put other items to make the whole situation trend toward a balanced load.
The nature of your question reminds me of the Nova Craft Supernova. The seat position in that boat is pretty far back for a solo canoe, and I've heard that the reason for that is so that a person can put one large pack in front of their knees without making the boat front-heavy. I moved the seat on my Supernova forward to a more "normal" position so the trim is right when paddling without a load, and I use the two-pack system to keep things balanced when carrying stuff.