Ross, good points needing clarification. (Use the same link above to view the additional 30+ pics)
- The bench seats are indeed taller on inside edge vs outside edge by design, approx 8" on inside vs 6" on outside edge (measured on outer edges of box), but not due to boat floor as it's perfectly level/flat.
- The bench seats do not get wider as you move aft, they are approx parallel at 13". The aft edge, however, is "angled"........ where the forward edge is squared off to match well with the front seats. I'm glad you pointed that out because the picture I took of the aft edge was taken at the angle which made it appear to be longer at 14". I took additional pictures... compare pics 83-86 and you'll see what I mean. There is a tiny "flare out" only on the top piece aft on inboard side.
- You're right... there are glassed in bases for the seats to lock into. The channel fits over the front edge and then the aluminum tube locks into place aft. A lot of leverage is placed on the aft tubes when the seats are tugged on to lift/get them out... definitely reinforce those if you build it the same. I can tell they've been pulled out before on this boat. The seat backs do feel relatively sturdy, just because they haven't been abused... but I can tell that this is an area I'm going to have to be careful with/ask passengers not to lean/pull on getting in/out of the boat. Kind of like not letting people grab the windshield to pull themselves up out of a CV, CVX or GT seat... it's sturdy enough, just can't afford to abuse it. The last measurement picture is how far back the front seat base is from just below the dash... so you can get an idea of placement for those fore and aft.