I've had very little time to work on trailer, so the ultra slow progress continues. I've covered the upper part of the box with 2 inches of hard foamboard. It has been quite tedious. Around here, the weather is too mild to buy big sheets of foamboard, so I've had to buy 2 Ft x 2 Ft x 1 inch panels and glue them up before attaching to box. My craftsmanship leaves much to be desired but we're getting there.
I plan on shaping the foam to a more tortoiselike form and than covering in fiberglass before painting.
Here's a couple of updated pics.