[slomotion]

Just something to think about.....if you put in tongue and groove decking with a steel frame around it, contrasts in temperature, and humidity may cause a problem later on because the wood won't have room to expand and the potential for buckling exists. In addition to that, if your going to use it, what will you use as skid strips?
I'm not trying to rain on your parade, just don't want you to go to all the expense and time to build the deck and have it disappoint you later. It needs to "breath" and be able to expand and contract. Even totally sealed the wood will want to move and you're dealing with a much larger area than a pickup bed.
It's going to be a good looking outfit when you're done!