Re:FRP Board cutters "These work wonders"
I've found the best tool for cutting FRP is an angle grinder with a cheapo diamond wheel. If you use a tablesaw, make sure the blade has lots of teeth (triple chip blades are good for it), and make sure the thin FRP can't slide under the bottom edge of the fence, or it will get screwed up. For outlet and switch boxes, I cut them out after the FRP is done with a rotozip and drywall bit. I just level down to the floor from the center of the box, make a mark on the floor with my sharpee, and write the measurement up from the floor to the center of the box on the floor too.