Did it with a Triumph Tiger shield a while ago.
Mark it with masking tape and cut it with a Dremel or similar. Very fine wheel, very fast and very slowly.
Advice I got was to do it when its as warm as possible in direct sun and you shouldn't have a problem with the plastic splitting.
The plastic will melt a bit with the speed of the wheel but it cleans up nicely with some abrasive paper.
Good luck
Chris
