ORIGINAL: Robotech
That's exactly what I did. Made a backing ring of lite ply, drilled the holes and filled with epoxy. After it dried I tapped them out to 4-40 and it worked out great. I do have to use a small srewdriver to get the plug out but I'm sure it will loosen up with time.
That is why I put a little Vaseline on the O ring on mine from time to time.