Rear Ramp door for foamie?

[Johnny Swank]

Anyone have a good idea for a rear ramp for a foamie? Now, would a 1” foam sip work for a ramp? Figure 400 lbs working weight on it at the most. Plan to stick with 4' tall cabin (thus maybe a 42"ish door) That's pretty steep, and I may have to go 5' tall in the back and taper down to 3' in the front to get a longer ramp.

Background:
I (poorly) made a foamie benroy about 12 years ago and plan to make a 5x10 square drop cargo trailer now. 2” foam walls and roof, PMF pre-applied inside and out then put together with 6” fiberglass tape and epoxy. Putting in a few spars with vertical1x2's running to the floor to act as hard tie off points and help with interior bashability. These interior vertical 1x2's will likely get tied into an exterior roof rack made with Unistrut or 8020 extrusion at some point too.

Trailer is an ancient Northern Tools 4x8 that we'll rehab with new bolts /paint etc. I'd like to replace the tongue with 2" tubing and add about 18" length as well. Planning on a 2" DIY SIP floor (1/4" ply on top, luan on bottom, and probably the same for the back wall to help with racking. The floor is complete overkill, but will help with trailer flex. Frankly a little worried about this thing racking given no interior wall

[GPW]

...???