Hell, Bison and a couple others have been 9's on a stock short block. The parts can take it (whithin reason) it's just you window for screwing up gets MUCH smaller. You make a mistake with the tune running 13's you may eat a HG, make a mistake or something happens trying to run low 10's, or a 9sec pass then you're probly picking a crank up off the ground.....or worse.