Here is a rough draft of the design I am considering:
I have not figured out the exact placement of the the axle yet.
As scaled in the pic the trailer is about 6' tall at its highest point. To make it a true stand-up for me I will have to make it a few inches taller or drop the floor below the high point.
The door will be between the porta potty closet and the bunks.
I still need to figure out how and where to add a little storage (next to the door, under the futon, between the porta potty closet and the trundle bed and/or above the trundle bed).
I also need to estimate the weight.
Any ideas and/or suggestions would be greatly appreciated.