I've got it! Very nice method. I'm already tempted to just go for doing it this way rather than making a mandrel to mount the old flywheel on and machining that down etc.
There is time to think about it now, I won't be doing it for at least a month or two.
Thanks again.

Two more questions:
1. How are the six prop retaining screws drilled while the hub is still in the lathe chuck?
2 Should I make up a drilling guide first? Out of some thick steel plate or round stock?