Was talking to my neighbor yesterday... showed him my new inspiration trailer, the Pikes Peak trailer. We talked out a few options and plans.
1: since my trailer frame is 50" x 62", a standard plywood won't fill the entire frame. Answer: lay out the plywood sideways, cutting ~31" X50" pieces and lapping the seam along the center brace. He's supplying plywood since he's got a ton of it.
2: I want the box to be detachable. The corner angle pieces will be bolted to the frame from either side. 8 bolts holding the box down should do the trick. For sake of overbuilding, I'll use Grade 8s. He already had 2" angle in his garage, so I've got that.
Not sure how I will tackle the lighting just yet. I think I might widen the rear and front of the frame and tie in the fender once I get the 3500lb axle on there. This would give me a steps and/or places to mount jerry cans, propane tanks, etc, without taking up space in the box. Something like this...