Very close Vandy, crank end tapers are usually 12deg included angle(set compound to 6deg but check with a dial indicator your on centre) but the diameter varies.If you machine the taper down you will need a new TCT tip to get under the case hardening, then the machined taper isn't hardened, but thats no worries if you have a generous radius where it steps down. It's a common misbelief that the woodruff key 'holds' the flywheel/rotor in place, this is just for ease of assembly at the factory.Vandy you are 100% correct that the taper hold them in place,just after machining lapp the shaft and new tapered flywheel with valve paste(at last a good use for 4T stuff).Machine the flywheel if possible.