Im rennovating a bass that a friend of mine has donated to me. It's quite old, probably 60s - 70s. I've already had to drill out a screw to get the scratchplate off, but I'm facing a much harder problem - the 4 screws for the pickups have had their head's worn off. I've tried drilling them out, but all that's done is melted the plastic pickup covers. I've also tried hacksawing a groove in one so I can use a normal screwdriver, but with no luck. The pick ups are fairly good, so I don't want to break them out. Has anyone ever experienced this problem? Could anyone help?