hi pete.
i built the enclosure out of 1.5 x 1.5 square, then screwed 1/2" ply to the outside. for waterproofing i first sprayed a coat of polyester resin, then one layer of matting with polyester resin. to colour it i sprayed the white gel coat. to mount windows i used a routed to "machine" 1/2" grooves. i'm going to stick plexi window in with silicone, then caulk the inside... i think it'll be pretty sealed. time will tell i suppose.
good eye on the tubing bender. i just finished a cage so it was not put away. it's safely away now. i race cars for fun so it comes in handy when i'm twisting tube. here's "the office" in my current car:
