so I purchased my metal stock and its on its way to my house, i went with the 3/16" (~5mm) thick aluminum 6061. It was like $160-170 for a 2' x 4' piece. So we'll see how that works out. I have all the dimensions worked out, still working on a good mounting system, the one posted above looks pretty cool, and easy to do. Once I get this done, I can post some pics of it on and off the car with weight and everything, and let you all know how much it would cost to fab up a few more of course you could pick the material.