Hef or his son Rapid Rewards. Both had major winning calves last season out of Heatwave heifers. Hef and Rapid Rewards are supposed to be calving ease bulls. If you want a 50% char composite calf look at Wrangler, Ledger. Cooley Royce gave me vigorous <70 lb calves the times I have used him, with dainty, halter-horse muzzled heads but he is known more for the production oriented side of things. After first calving you can look at Firewater to produce a registered 16/32nds charolais composite. You want something shaped like a snake when it slides out, not shaped like a brick. The length of the long bones won't be your issue, rather the size of the jointy structures like shoulders and hips. If the neck is short and squatty, add the head to the dimension of the shoulders.