Excellent project !
Have you finalized the techniques/ materials you will use for the "box" part ? What makes this especially nice is all edges radiused with no visable seems and a compound lid (as your sketch) . All possible with one-off fiberglass/epoxy and a foam core. Light weight too. You could build all the panels except the lid on a flat table and use 1/8" birch plywood for the inner skin for impact resistance and then fiberglass the outside after you glue the panels together and do the radius. I bet if you used epoxy with a filler to glue the panels together and also to glue the plywood skin you could go without a fillet in the interior.... For the lid I would check out the Teardrop Trailer guys and see how they deal with the hinges and weatherstripping etc.
Just a thought if you haven't already decided on the method/ materials for the box.
Also thanks for the videos on compounding sheet metal. Some of those techniques are new to me .