You've suggested a very good option. Newfound Woodworks sells half-inch thick foam wedges with their seats. I used them under a Surf to Summit Grande seat on my Merganser. I'll be posting a photo of the result later today on my blog site at http://twofootartist.com/merganser-construction-notes/

Twofootartist,

I saw your photos, and I can duplicate that by cutting my 3" foam on a slight angle on my band-saw... should give me plenty of center-line padding to stablize the seat.

Wow, nice ride you built there!  I'm stealing your (and other's) idea for flush hatches, I don't dislike the buckles, but would rather keep everything clean/neat if possible.  The hatch-hooks you made look better than anything I've seen to date, so I'll be using your design (let me know if there's a proprietary fee!).

Thanks for the tip/reply,

Larry

I stole the hatch hook design from kayakkev, who borrowed it from someone else. Some people have the hooks facing inward, but it's easier to release the bungees with the hooks facing outward. Mine were cut from 6mm okuome plywood. They are two inches high. Next time I will make them 1-1/2" -Wes