It sort of sucks but on the positive side it's a confirmation/revelation that the compression from side sleeping is a major factor in my TOS, and one that I can hopefully eliminate. Given that I have this condition, it's always good to find something to improve.

Regarding tips, one that I saw somewhere was to start on your side but then twist your shoulders back, using a pillow underneath the far shoulder for support. The idea is that you get some of the comfort of side sleeping while taking that compression off the shoulder that would normally be underneath you were you truly on your side.

I've tried it for brief periods of time and it seems okay. I worry that I could go back to side sleeping easily. I also wonder if having the torso twisted like that for a long period of time would cause any problems.

Btw I just made this decision today. So I've yet to see how well I fair with my attempt. But I'm committed. There is no longer any doubt that side sleeping has to go.