Haha yes I think diamond plate may get too hot I just plan on putting a rubber mat up there. I had extra diamond plate so if figure I'd atleast use it. My cost was about 500$ in materials, $250 in shop supplies( welder gas, rivets, electricity, etc) and labor was looking to be about 1200-1400. But ...

Here some pix of my dog box a buddy and I built for my t100. Steel frame with diamond plate.

http://i68.tinypic.com/30b1pnq.jpg

http://i68.tinypic.com/30bk9kj.jpg

http://i67.tinypic.com/zvdavr.jpg

If u want a box like this let me know and we can have one built for ya. We can do several ...