So after a day's worth of research I have come to the following conclusions:
1. Carbon will be too abrasive inside an alloy shock body and will also absorb oil
2. Nylon 6, Nylon 65 and Nylon 66 also absorb oil and do not machine cleanly
The magic material is Acetal! Acetal provides high strength and stiffness coupled with enhanced dimensional stability and ease of machining. As a semi-crystalline material, acetal is also characterised by a low coefficient of friction and good wear properties, especially in wet environments.
New pistons here we come!
