Geoffrey W. Schultz wrote:

However, I really don't have any experience machining plastic,

The most critical factor is a scary sharp cutter. Certain carbide
inserts work quite well if they are uncoated and of the
positive/negative type e.g. TNMP-321. You can hone these on a fine
diamond hone. Otherwise, a carefully honed HSS cutter.

Nylon
UHMW

I would choose one of those.

Comments on the machining qualities, UV resistance, and overall strength of
these would be greatly appreciated.

Could you avoid the UV resistance problem by placing a thin walled
stainless shield over the bearing area? Attach it to the mast but have
it not in contact with the bushing.

Ted