So the overflow/safety drain of my tub rusted away, I got a replacement, but can't put it in since the bolt that held it to the PVC fitting is all rusted. I So I'm all out of ideas, I tried WD-40, vice grips, special striped screw remover bits, heat, drilling a small hole into it (no dice as there's too much flex/play), praying, cursing...
Aside from having to break the wall on the other side to remove the fitting, is there anything else I could try?