dremmel. use the cutting disks. Worked best for me. Just take your time. You can drill a hole in the middle 1st
if you use a dremel..use a real 'gas mask'. when you dremel carbon fiber it obviously makes carbon fiber dust..which is dangerous to say the least.
they sell carbon fiber sheers, u.s. composites sells them as well as practically any place that sells carbon fiber for fabrication purposes.