those rparts lids look so much like what I have been making. I am even using identical
hinges (west marine table
hinges). Only thing is that my lids are four inches thick and made of styrofoam (blueboard). The top is routered out 12" wide oak boards. I am still not finished... it is a lot of work getting the stepped sealing surfaces to fit good with the box opening, lots of fiberglass sanding.