I WENT WITH STEEL. BOUGHT THE FRAME 6.5′ X 10′ WITH 3′ V. I REALLY ONLY WANT TO HAVE TWO PEOPLE MAX IN IT. I MODELED IT AFTER THE ICE CASTLE GRANDPA’S HIDEOUT? I KNOW PEOPLE TALK ABOUT RUST, BUT I COATED MY FRAME WITH THREE COATS OF HURCULINER (SP) BEDLINER FOR TRUCKS. BEEN 3 YEARS AND NO RUST YET. THE ONLY THING I WOULD CHANGE IS I WOULD HAVE WENT 2′ LONGER. THEY SAY YOU BUILD YOUR FIRST HOUSE TO SELL AND YOUR SECOND ONE TO KEEP.