Proposed Foamie Build

I've been lurking around on this site since I joined several months ago, and I'm finally ready to show what's been cooking in my brain ever since I saw a post about foamies.
I'm about to retire - for the fourth time - and I just know I can't just sit around and watch the grass grow and the snow fall, so this may be a project post-retirement.
The cutout on each side of the bottom is so it will fit on a 6'x12' trailer that has side rails.
I've pulled the nose out so I can have put a king sized bed in it and still have some floor space.
Any comments, suggestions, lessons learned about width, height, and length would be appreciated.
I've got eight months to work on the design, and I'm certainly not an expert at this by any means.
I'm about to retire - for the fourth time - and I just know I can't just sit around and watch the grass grow and the snow fall, so this may be a project post-retirement.
The cutout on each side of the bottom is so it will fit on a 6'x12' trailer that has side rails.
I've pulled the nose out so I can have put a king sized bed in it and still have some floor space.
Any comments, suggestions, lessons learned about width, height, and length would be appreciated.
I've got eight months to work on the design, and I'm certainly not an expert at this by any means.