I've decided to get smaller pads before I go to a rotary. I've been using 6.5 inch pads on my PC. I had originally planned going down to 4 inch pads since they will correct better. After looking on a few web sites they really make it sound like they 4 inchers are really just for spot fixing and not doing the whole car. Is this true? Would I be smarter to go in between and get 5.5 inch pads? I want to be able to get some pretty deep swirls out of our mercedes GL450. Which should I go with?