Can't even install it - Radical Firearms M-LOK Hybrid Rail System (MHR)

When I went to take out the one retaining screw so I could unscrew the barrel nut and actually install the hand guard, the retaining screw was stuck in there so badly I stripped it trying to get it out! I've tried all manner of ways to fix it, including heating it up with a propane torch to see if the metals expanding at different rates would break it loose. I've emailed the company to see about swapping it for a new one, but seeing how Radical Firearms let this one out the door in the first place has forever deterred me from buying anything they make ever again.