The only thing I can think of is one of the small easy out tools. I've used them to get stripped screws out before

How about trying the next size Torx bit, If it is close but won`t fit a few tap`s of a small hammer might drive the torx bit in to the head of the Trox head screw enough to get a good bite on the screw, just hope there's no Loctite on it. If so you need to heat it up to about 300 deg. My 2 cents.

Talk to Andy at Skinners. He may have a solution.

put a little heat to first. there is a reason it stripped.

with variable speed and reversible; install left hand drill bit and back it out. If it doesn't catch, go up one size bit. If it doesn't work, you have at least removed the center section of the screw and that should've reduced the radial pressure on the threads, making it easier to remove with other tools.

Doesn't need to be red hot; just past where you can touch with bare skin.

Carefully... this is very easy to screw up.

I've had a few Number 1's but it's been a while. Best I remember they have a sight rail that's bolted on and I'm guessing you're trying to get one of those screws out to mount the skinner sight on. If so, take out the other screws, use a healthy dose of penetrating oil. Removing the other screws will loosen the rail and penetrating oil will, well...penetrate. That might let you work the rail back and forth...even a tiny bit of left and right can go a very long way. Another gunsmith/mechanic trick you might try before or in conjunction with the above is to take punch and a small hammer and smack the screw straight down. This is an old school trick for seating threads if you want more torque on a bolt...tighten, rap with punch, now you can tighten more, OR for opposite effect, it's useful for removing a stubborn screw. It won't work on locktite though. For that you will need heat. A hair dryer can work sometimes, a soldering iron with a clean tip works really well, and an industrial heat gun will work as well. If Locktite is involved, once it's hot enough to screw out, you'll smell the Locktite (sort of a sweet smell). Even if Locktite isn't involved, getting the area hot can help and sometimes getting it all hot and letting it cool works. If none of that works, go with what John K said. A left hand drill bit can work wonders but use a centering punch (an automatic center punch with a sharp tip works great) and get it perfect. You definitely do not want to drill into the threads.