Backing pads are changeable I have mine set up for 8" and the picture is my air buffer the one like it for grinding is at work but not much different in RPM's
I was thinking you might would be interested in what I'm thinking of doing to my trunk and floor boards and maybe the under side of the car. Was gonna use pick up truck bed liner you can tint it any solid color you want so lime green you can do. Not going to be spot on to match the out side of the car but close I think. The good thing would be you don't need seam sealer no having to feather the paint out and just poor-15 the rusty parts sand the paint with 80 grit or good wire wheel or fiber disc, etch prime the bare metal if very much and easy to spray.