I bought a c270 from Target and printed the original model. The faceplate at 100% was just fine. The focus ring at 100% was too big to properly grip the c270 focus wheel.

If you scale the focus wheel to 97%, it will grip the focus ring, but its too small to stay in the face plate.

So i took the original focus ring into Blender, selected the inner nodes and shrunk them by 97% but kept the rest of the focus ring at its original dimensions. So you get a focus ring that grips the c270 focus wheel, but also securely snaps into the face plate.

You need to use a little force, but it will go into the plate and around the focus ring.