I have a problem with my tub overflow. The stainless steel cover plate screws that held the overflow cover plate to the bronze overflow pipe have corroded away. With virtually no shank to extract them with locking pliers, it appears galvanic corrosion has frozen the threads. Replacing the overflow pipe is not ideal because I would have to remove the water heater first to gain access. I'm thinking I might be able to cutoff the exposed screw shank and redrill/tap new threads. Has anyone done this before and/or offer some recommendations? Thank you.