You mean the screws made of Chocolate? Those are soft on all motorcycles.
Prevent if possible, using a high quality screwdriver does wonders. People swear by the JIS #2 (that'd be Japanese Industrial Standard), but I've been using my Snap-On #2 successfully for 11 years. Others have had good luck with your standard drywall bit. Then there's technique, torque is cumulative, so don't put a Ton of force on the screw and have it strip (which is the point behind an impact, a sharp increase of torque), but hold it tight for long enough and it Will break free.
After it starts to strip, that's the time to try an impact (sounds like you're here now) with the properly fitting bit.
And once it's so far gone that there's nothing left to hold onto, then you can try your choice of EZ-outs, screw extractors, left handed drill bits or just a normal drill bit. When choosing a drill bit, pick one that's the same size, or slightly smaller, than the Shaft of the screw. All you want to do is drill off the head, the threads will unscrew by finger once the tension is released. No reason to ruin the cover or MC, just go slow. I'd had to do this probably a hundred times in the last decade (mechanic), enough that I bought a box of 500 replacement stainless allen screws just to always have on hand.
Good luck, it's annoying but not hard.
