seat height
A seat hung higher (say, directly to the inwales) will give you a canoe that is a bit more unstable (tippier) than a seat which is hung a few inches lower, using longer hanging bolts and spacers.
There will be a bit more room under a seat hung higher, giving the paddler a bit more foot room when kneeling, and the higher seat will support the kneeling paddler in a somewhat more upright position – a more comfortable kneeling position, in my opinion.
A seat hung lower will do just the opposite – less foot room and a somewhat lower body position when kneeling, leading in my case to knees that have become reluctant to straighten out when the time to kneel ends.
A stern seat hung just under the rails will also give the stern paddler a somewhat better view forward. I have seen canoes with the rear seat hung to the inwales, with the bow seat hung lower, presumably for this reason.
In small, solo paddler canoes (see some of Platt Monforts geodesic canoes, or the Sairy Gamp Rushton built for Nessmuk or other of Rushton’s canoes), it is not uncommon for the paddler to sit directly on the floor of the canoe (or on a seat or pad only a couple of inches high), often paddling with a double-bladded paddle.
Another consideration is that a seat hung directly to the inwales will act as a structural thwart, giving a bit more rigidity to the hull, whereas a seat hung a few inches lower has virtually no structural value, and may allow the canoe to spread just a bit. Compare the seats in my OT 15’ 50 pounder (as bought) with those of Benson Grey’s, which was built several years earlier, and which are attached directly to the inwales (except for a small spacer on the stern seat to level the seat).
Note that the ends of the bow seat rails on mine are some distance from the ribs of the canoe, which have spread a bit over the years. When the canoe was built, the seat rails would have abutted the ribs, as those of the stern seat still do, and the bolts and spacers on my bow seat would have hung directly down, perpendicular to the inwale. Though not really in the photo, they spacers now are slanted a bit, and the seat is not stiffly hanging from the inwales, but rather can wobble a bit with the spacers having been pulled out of alignment.
Like everything else in canoe and boat building, almost anything you do involves trade-offs and compromises. Someday I will probably experiment a bit -- it is not hard to raise the seats, and not hard to lower them again if I find I like them the way they are.
