I don't see how the Sheldon fixed-cup method could fail short of the bolt breaking. It takes a LOT of force to break a bolt that big. Something has got to give -I'd put my money on it being the fixed cup. If you don't have a big enough wrench get another bigger one or go with a big 3/4"-drive air impact driver. Either the fixed cup is going to move, the bolt is going to snap, or the BB is going to twist off the frame...