Jack, I'll make the obvious comment in case someone sees this picture and isn't aware of the limitations imposed by that setup. I recognise that you know about the issue, but others may not.
Because this is a built-up crank made out of multiple pieces pressed into each other, aligning the two sides of the crankshaft (flywheel side and output shaft side) is done very carefully with V blocks and indicator, to get the two sides into alignment so they can run in the engine's main bearings. Consequently any torsional load applied to the tailstock side while the crankshaft is held in the chuck, might twist one or both ends of the crankpin where it is pressed into the webs. This would cause misalignment of the flywheel shaft relative to the output shaft. That could be corrected by setting up the crankshaft again with the V blocks and indicator, but any machining you had done in the meantime on the tailstock side of the crankshaft, would then run out of true. With this type of setup you can only perform conventional lathe-turning operations on the side of the crankshaft that is held in the chuck.
