Otis, sometimes you can get a small flat screwdriver and file it so it just fits into the allen set screw but with force. Spray a little lube or Liquid Wrench on it and slowly try to back it out. You can put a wrench or pliers on the shaft of the screwdriver and help with the torque, while pushing down on the handle. The fit is the key to it. Good Luck.
ps. All else fails you can drill it out and re-tap for a larger size. I don't think an easy-out will get deep enough to get purchase.
I scanned your post. But; I have had this problem occur before and was able to use a drill bit and an "easy out". Small hole drilled in the center and then an easy out. Another method is to drill out the screw with a drill bit the size of the hole. Then re-tap the hole. Once I was able to drill out the screw and "self- tap" the hole with a new screw. What this has taught me and what I have tried to emphasize to those who have brought such a problem to me for repair is; Be careful and go lightly in the future.
Steve Albin is "way over the top" with regard to any kind of repair or glassing issue in No. Orange County. Aloha Glassing ----------next door to Foam EZ.
There are such things as left hand drill bits, I'd like to have some for touph jobs like this. Easy out work is very touchy, you're lucky to have the starter hole already there. Thats a stainless screw, very touph to drill in stainless, start with a sharp bit and I'd drill all the way thru if the sticking the bit to back it out doesn't work. Use an easy out that is small enouph to fit deep into the new hole. When drilling the screw be careful about heating things up so much that the surrounding plastics melt too much. I'd try all the tricks first that prevent needing to do the drill work. Somebody whos done this before will do it kind of easily but the first time will be touchy.