Cyclops, since the Vulcan is basically a flying wing you'll both want and need to use a wing airfoil with some reflex rather than a flat bottom wing with a strong camber value. That wing airfoil will act like you're holding a lot of down elevator in it.

I'd suggest you go for the pretty much scale symmetrical airfoil with some washout and reflex at the tip airfoils. In fact for a change even with a 48" span the chord will be so large that even at moderate flying speeds the Reynolds numbers will be so high that you will get away with the super thick root airfoil even with the funky inlet leading edge.