An alternate method to locate the seat is to use the scale provided by the canoe itself -- the ribs. As may be seen in the pictures of Fitz's canoe (1965) above, of my yellow canoe (1931), and of the blue canoe (1914) that Benson Gray restored and for which he posted pictures
(
http://forums.wcha.org/showthread.php?t=3968), the aft edge of the bow seat is at the 8th rib forward of center. So that location of the bow seat has withstood the test of time.
However, you might note that in Benson's 1914 canoe, the seats are mounted directly to the inwales, whereas in the later canoes the seats are hung from the inwales and are a bit lower. Mounting the seats directly to the inwales provides a certain structural rigidity that is missing when the seats are hung from bolts (the gunwales on my 50 pounder have spread a bit, so the seat hangers are splayed a little, and the decks are no longer tight to the inwales), but makes for less stability. I seem to recall seeing a picture of at least one 15' OT which split the difference -- the bow seat was hung, but the stern seat was fastened to the inwales -- I don't know if this was done at the factory, and I can't locate the picture.
Rollin Thurlow advised me that the stability gained by lowering the seats is desirable.
I believe that it is standard to have only one thwart, the center thwart, in an OT 15' canoe with seats. Having additional thwarts (except small carry thwarts) would result, I think, in an awkward layout, and could make it difficult to paddle solo from the bow seat while facing the stern. But a thwart layout using two thwarts without a center thwart might be managable. But then it would be more difficult to carry the canoe on your shoulders -- can't do anything without trade-offs.
I have aready made small carry thwarts like the ones your canoe has and plan to install them soon, in hopes of stiffening the gunwales at least a little, as well as providing a handy place for attaching painters.
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