A finished rear hub weighs 6.5 pounds. I wouldn't worry about getting a forging. You won't be able to get it forged close enough to the net size to see the forging marks when you are done anyway. A billet will weigh 51 pounds for a rear hub. You are just asking for a ton of grief. If you are really crazy, I may be able to find some of our old forgings around here.
When the rear hub breaks it snaps at the root of the outer bearing (on the inboard side of the rotor flange). It is a catastrophic, wheel falling off, pants soiling event.
David
