Conal, if you think you can shoot 1" lead ball, work up to it. Ball mass scales to the cube power of diameter. A 1" ball is 2^3 (i.e. 8x) the weight of .50 and (1/.375)^3 (i.e. 19x) the weight of 3/8" shot. Band strength must be scaled to mass to get comparable velocity so you scale width. Imagine trying to pull 10 or more sets of Express Bands, Fastbands, or Gold Winners. You could of course just shoot the strongest band you could draw and make do with poor velocity. There is a major caveat though. Your cnances of a fork hit rise dramatically and with the great energies involved, that may translate into an injury that may maim or kill you. There is another phenomenon common to big projectiles too, called the 180 degree shot where the pouch flips over and shoots the projectile into your face or chest with more or less full force. It's more than folly, it's positively reckless.
So as I said work up to larger shot slowly and hopefully have the good sense to realise when you're about to reach the danger zone and pull up short of it.