It hit me today at work that the best option for a floor would be tubular crossbars with a bolt on floor made out of .120" thick black nylon. I mill this material extensively at work. I would suggest it be made in 3 sections with holes milled/drilled in it every so often for hooks and straps to be placed. To attach it I would use U-bolts. Simple, easy, effective.

If you used expanded metal it would be to abrasive. Not to mention the 200 tack welds used to attach it. And to top it all of you couldn't clean the roof, and it would look tacky.

Good Idea but I like mine better.

Just my .02c though