I'm going to cut some plexi this week.
Oscar gave a tip the other day to use a Template router bit with the bearing at the top, then you just put the plexi underneath the CP, pop the bit through the plexi (plunge router), and make a few circles, then move on to the next hole. The template bit bearing keeps the bit inside the CP hole without hurting it, and just the end of the bit goes through the plexi exactly the shape of the hole.