I took a flat head screwdriver just slightly larger than the original stripped out phillips slots (original was a PH0), placed it firmly on the head of the screw and rocked it back and forth from corner to corner for a while until it had formed enough of a groove that I could carefully unscrew. I had two very tiny screws with the same issue, one of them I had tried to drill out first with no success, and the other still had vague remnants of the original slots. The drilled out one took longer than the other one for this to work (used a 2.5 for the drilled out one, and a 2.0 for the one that was less stripped).