If a bull is structurally sound he can breed just about any size cow-i've had the odd 2600 lb or better Charolais bull get a 8 month old heifer bred-a bull should be an athlete. Those bad legged-over fat pukes that need a two minute rest between mounting and punching her ticket are the problem. You'll find that most broken penises come from those types of bulls too. It makes it easy selecting bulls-if I don't see a good stride and good feet and legs I just x them out in the sale catalogue and move on.I think posts legged bulls are the worst-they seem to get sore backed and more clumsy as the season wears on.