Don't really have plans...but these pics will reveal really how simple it is.
Some bullet points:
The angle iron is self-tap screw bolted into the frame members for obvious rigidity.
There five of them - two on the flanks - two small ones on the corners (it doesn't matter if they follow "the bend" in the trailer or not) and one along the center under the main front window.
2x4's bolted to them.
Plywood flanks not screwed down to allow access to pump, H2O tank, etc.
We are still making curtains - AND - the rear backrest will be simply a mattress topper with cover that is rolled up during the day. At night, it will unroll to cover the seams the cushions create.
The table column I think I picked up at Hamilton Marine - or any search at a marine supply will render a telescoping table column. That was the most expensive of the whole plan... I think about $200 or so...
Let me know if you have questions.