Wouldn't you know it my camera batt is down but what I did was 1st was I put in a piece of balsa stick 1/4 with a piece of light ply over it and glued it to the weak area on both sides the fuse that always seem to crack. Then I glued a piece of light ply on them. I wrapped my batt in foam and zip tied it the the plywood floor that i made.
When I cut the covering out for the hatch I used the covering for a template for my light ply hatch cover. I also glued some light ply pieces on the inside bottom fuse for the hatch cover to rest on and screw to.