There is a guy on here that mated up a VFR 800 { i think} rotor to the Honda crank to give him more charging power for his fuel injection set up, all i know is that it was heaps lighter and produced a lot more power than the standard rotor and if i remember correctly, it was then possible to remove 18mm from the alternator cover. The guy that did it put a spacer on the crank to make it sit in the correct position for the stock cover.
Mick