Well I know it's been 2 1/2 years but I've only just found your build thread. I used to be active on this forum when I owned an XJ but haven't had a look here for many years.
Nice camper build
How's it holding up over the years? Did you ever put it on an offroad trailer? Steve F's build was one of my inspirations and yours is excellent too. I hope to put my own camper box on a trailer when I'm finished to give me more flexibility. Great for standard campground holdidays.
My camper box will slide in to my ute tub and I'm using the same boat building techniques as you did. Epoxy glue, fillet the inside corners, glass the outside and waterproof the whole thing. I don't know why more people don't build this way as it's hugely strong and doesn't need all the framing that usually goes into camper and teardrops. Check out my build if you are interested at
http://myswag.org/forum/index.php?topic=11381.0
Cheers,
HB