Steel studs are a great idea, they're very lightweight and should be just the right strength. Paint them even if they're galvanized, the galvanization on them usually is pretty worthless in my experience.
Threading fasteners into those holes is a great idea too.
Got 25.2mpg at 65mph going up to Dallas. Ended up carrying a mattress and some bikes on the back that dragged it back down. Got close to 24mpg on the way back home with only 2 major accidents to drag the traffic to stop and go and my quest fer 25mpg.
I can easily say that my T-100 definitely coasts better than it did before. Didn't git the downshifting going up the hills like it used to.