Well I had to try it (carving PVC) and decided to make myself a new sign. This will be the top half for the sign.
Since I went with conformed outline text and a ribbon banner pattern (jpaluk) I also opted to use the 3/16" carving bit as the pattern bit. Finished carve size is
9x28 and took 3 hours and 20 minutes @ best carve quality to carve and cut out. At optimum it would have been 6hrs +. Seems like it was posted that with the 3/16 bit we should only use best as the highest setting. Tried doing a search on that but was unable to find anything on it.
Found out how big of a mess the PVC is to carve. Even with dust collection I had to pause the carve about 6 times to clean it out some with the vac. Also used a wire brush on the rails and bearings in order to get it off. It really packed and stuck to the rails.
The conceptual picture of the design is some what of what the final will look like.