Looking at the directions for the application of 3M 5200, it says nothing about surface preparation. I.E. scuffing or removing paint. I have a 4"x4" piece of 3/4" plywood I painted on both sides with primer and 2 coats of latex paint. I plan on attaching this plywood to the inside hull to attach a heater. My question is do I remove the paint on the side to be bonded or leave it painted or does it matter?