I don't know a great deal about the technology, but i gather that fuel tanks in F1 cars are rubber based (i assume silicon rubber to stop oil corrosion). I imagine they are pretty light, as well as being extremely damage tolerant. I'm guessing that the rubber is used as a resin for composite contruction. The likelyhood of tank leakage/puncture, and all the unpleasant consequenses, would thus be much reduced...
What is the latest in heli rotor vibration damping? I promise not to do any controversial calcs!
Mart