If you want to discuss Geno's possible frail build holding up running to often, thats a very valid point but the thing about the pistol is the fact that elusiveness is actually not important, because if run correctly, the QB has only 1 man to beat and its in the open field. If the DE freezes, and the lane is there, its actually a rare situation where straight line speed is more valuable than "3 cone" quickness.
Yeah his frailty is probably one of my biggest arguments against it, and one of the reasons I don't like the read option to begin with in most QBs unless you are built like Logan Thomas.
I think with our lack of elite WRs, the LBs are going to step up too often, and Geno doesn't have the speed to outrun them like RGIII or Kapernick. And two, one of Geno's biggest problems is fumbling, and I'm not sure how good he will be at holding onto the balls when he gets hit.