Mark, I'm putting the last coat of varnish on a five yr old Coho that a friend and I use,,so far it's my touring boat for carrying lots of stuff. Started with one layer of 4oz glass, now that's it's been knocked about for 5yrs of constant use I sanded down into the glass and added another layer all around,,oh boy a heavy boat again!. But I don't mind slowly grinding onto rocks with a loaded boat now.

I've got a few seats that came out of Chesapeake boats that I made from 3" minecell that was cut into two parallelagram blocks then reglued and carved. These seats have gone from one boat to another and now to this boat. The angle isn't perfect but it works fine,,try some salamander hip pads to fit out the sides and jam the seat down into place. I don't find the use of velcro worthwhile,,anything held by velcro in the bottom of a kayak will come up eventually and not when you want it to. Things should be mechanically held into place so 100's lbs of water can't pull it up. Occasionally I'll toss in the thermarest pad and deflate it almost entirely,,a very, very comfortable set up.