Gonna be for a 12" BM and trying to save as much room as possible.
An idea I came up with is:
38" W (max)
33" D (max)
7" H (max) - This is from the bottom of my trunk to the top of the opening area.
Max internal height is around 17" or less.
Thinking it might be more like a "false floor" where the false floor is the entire box.
Hopefully you guys get the idea.
Oh and I rather go ported, don't want sealed.
Will pay a few bucks for a good design