Started my car first time. Two bucket wash clayed it taped everything off and went to start the test spot opened my new porter cable but it says on one of the pieces Use 5" plate only, or something similar. Does this mean that I can't use the 3" backer and MF disc I have bought or does it mean I have to remove that part to use the 3" pads. Looking to finish the car tomorrow but it would be a lot of hand work if I can only use the 5" backing plate.