Bonkers, If you haven't taken your sills off yet, your screw holes aren't stripped. They get that way because they can only handle a tiny bit of pressure and everyone who re-installs them strips them. I'm not kidding, I don't think they can handle 1 pound of pressure. Here's what you should do.
1. Ensure you have the grey screws, they are coated unlike the original black ones. Buy new it not. 2. Remove sills. 3. Flatten holes with various tools, whatever works. 4. Test fit a screw back in with sill off and get an idea on how little pressure it takes before hole begins to pull as you'll be able to see it. 5. Touch up holes with POR15 and Qtip 6. Reinstall sills and use high temp low strength threadlock on screws so they won't back out.
works like a charm