New score, change of plans

So I scored a full size 6'x8' truck bed cap for free a week ago...

Sorry for the poor quality. I was losing light and the phone pinhole camera can't keep up.
Fiberglass, but of an older design. Someone thought it was nice enough to repaint at some point. It has all of the windows intact (real glass, except the plexi hatch), of which the sides slide open and are screened.. Perfect! However there is one spot in the fiberglass that was punched in from probably turning into something and needs repair (never worked with fiberglass but definitely willing to try by this point). I'd estimate it's around 200lb so not exactly light.
This is prompting a complete design change from the plans I put on hold of an ultralight explorer box style trailer. Life got in the way.. getting married soon, was laid off for several months but eventually found another job. I also lost my "primary" TV to a wreck in between all this, so I can make the next TV purchase more tailored to the trailer. Money is tight right now. And for free.. It's hard to pass up having half a camper already built. Can't afford a honeymoon so planning on this trailer being the alternative. Just trying to look forward to the future at the moment
Anyway so I have a bed cap, an axle that is waaay too narrow for it (from the HF 4'x40" trailer kit), 300lb springs that are too soft for the weight that this build will turn into (already reused the HF springs), and a tongue bar that I started welding up that may or may not work..
My current plan is to build out a wood frame to support the floor, maybe standard 2x4" or maybe glued together 1x" hickory boards to make 2x" (if I can soak the cost), and attach a metal tongue. Either bolting the 2x2" tongue bar that I've got to the wood frame, or scrapping that and making an A-frame that attaches to the spring support plates that will attach to the frame. Otherwise all I need to do is make a facsimile if a truck bed to attach the top to. A more appropriate length axle and heavier springs are inexpensive enough to come by so I'm not too worried about that.
Currently for shape I'm thinking of flipping the top in reverse, cutting out the "front" windows and making that area the spot for the door in the rear. That way I can just attach plywood to the front and back to do whatever I need. Which would make it different from the other bed cap builds I've seen, and give it a bit of a sloped back look.
I've already got a decent "full" size innerspring futon mattress to use that is comfy to sleep on. My idea is to keep with the futon idea and engineer the bed to bifold into a couch by pushing the mattress toward the front of the trailer.
Not a newb to DIY stuff.. Heck, a couple months ago my, previously spare.. now primary, vehicle dropped a valve seat and split a piston in half. Managed to get it back running having never opened an engine up except to do valve adjustment on a motorcycle. However sometimes I wonder if all this change in my life is messing with my head.
Thoughts?

Sorry for the poor quality. I was losing light and the phone pinhole camera can't keep up.
Fiberglass, but of an older design. Someone thought it was nice enough to repaint at some point. It has all of the windows intact (real glass, except the plexi hatch), of which the sides slide open and are screened.. Perfect! However there is one spot in the fiberglass that was punched in from probably turning into something and needs repair (never worked with fiberglass but definitely willing to try by this point). I'd estimate it's around 200lb so not exactly light.
This is prompting a complete design change from the plans I put on hold of an ultralight explorer box style trailer. Life got in the way.. getting married soon, was laid off for several months but eventually found another job. I also lost my "primary" TV to a wreck in between all this, so I can make the next TV purchase more tailored to the trailer. Money is tight right now. And for free.. It's hard to pass up having half a camper already built. Can't afford a honeymoon so planning on this trailer being the alternative. Just trying to look forward to the future at the moment

Anyway so I have a bed cap, an axle that is waaay too narrow for it (from the HF 4'x40" trailer kit), 300lb springs that are too soft for the weight that this build will turn into (already reused the HF springs), and a tongue bar that I started welding up that may or may not work..
My current plan is to build out a wood frame to support the floor, maybe standard 2x4" or maybe glued together 1x" hickory boards to make 2x" (if I can soak the cost), and attach a metal tongue. Either bolting the 2x2" tongue bar that I've got to the wood frame, or scrapping that and making an A-frame that attaches to the spring support plates that will attach to the frame. Otherwise all I need to do is make a facsimile if a truck bed to attach the top to. A more appropriate length axle and heavier springs are inexpensive enough to come by so I'm not too worried about that.
Currently for shape I'm thinking of flipping the top in reverse, cutting out the "front" windows and making that area the spot for the door in the rear. That way I can just attach plywood to the front and back to do whatever I need. Which would make it different from the other bed cap builds I've seen, and give it a bit of a sloped back look.
I've already got a decent "full" size innerspring futon mattress to use that is comfy to sleep on. My idea is to keep with the futon idea and engineer the bed to bifold into a couch by pushing the mattress toward the front of the trailer.
Not a newb to DIY stuff.. Heck, a couple months ago my, previously spare.. now primary, vehicle dropped a valve seat and split a piston in half. Managed to get it back running having never opened an engine up except to do valve adjustment on a motorcycle. However sometimes I wonder if all this change in my life is messing with my head.

Thoughts?