Using the template provided in Peco’s turntable kit as a guide, I put a hole in the module surface for the turntable. Having limited space for “real” tools, I used a hole-saw attachment for my Dremel. It worked well except the lock-nut loosened up early on, which made the hole a bit too wide.
I ruminated over this problem while laying down strips of 3.25″ x 36″ Midwest brand cork. Halfway through I realized that, if I used the scraps of cork to line the hole, I could sand it to the proper diameter. It worked perfectly. I covered the entire surface of the module with cork, then sanded it down to reduce any rough edges.