OK, I'm going to take a chisel blade or something to mine to help it flatten down better.  I never seem to be able to file down the edges of mine enough to get them to lay right, probably because I'm afraid of leaving visible gaps at the edges.  I paint and sort-of distress mine, often before I finish detailing the car.  I put sheet lead on the sub-floors, either before or after painting, usually before, and hold them down with Shoe Goo (or Zap-A-Dap, or similar), then I use the same cement on the back of the wood floor insert and press it down.

Ron Merrick