David,
milling the vanes may be very tricky and time-consuming (expensive) procedure.
It is much better approach to try and replace the vanes with thin shim or tape (.5mm and thinner bronze or messing).
You only have to think of the way to attach the tape to the secondary holder.
Another approach to reduce/remove spikes are curved vanes (
http://www.protostar.biz/cm-faq.htm)