Rob, for one thing make sure your dope is good and dry before putting the lid on. Sand around the edges of the lid and it's surrounding area so build up dope stays at a minimum. I used Windy's version on my latest.

One way to do it is to use amaple block for wing bolt attachment, threaded 1/4 x 20.  Use your dremel and smoothly concave the center of the block down leaving the threads about 3/16 thick .  Now build your plywood box with the maple block as the base.  If needs be, put a piece of balsa over the maple block to give contour, but uncover the center hole.  For weight, I use steel BB's dropped in through the threaded hole.  When finished, close the hole with a piece of wing hold down bolt.  All that shows on the outside is the piece of hold down bolt.