I finished the machine using the PETG rotor. It works great at 8,000 rpm, 20 ipm feed, 1/2 inch stroke but 8mm cut (sort of a slot).
I want to repace the PETG rotor with one made from 6061, but so far the printed rotor seems pretty durable. I guess I'll run it until it quits.
Amazinng techology. I have the utmost respect for the guys who thought of needle cutting foamboard.