forehand shoulder pain, does it have to do with the racquet/string setup?

[forehandbackhand21]

Hey guys,

I'm getting this top/side of shoulder and upper bicep pain when I hit forehands. If I hit in the center of the strings, I dont feel it much, but when I hit it slightly off it hurts, and when I shank its pretty painful. I feel it somewhat sharply right on the corner of my shoulder (feels like its on top of a bone).

I think it may be the rotator cuff, but the weird thing is, it doesnt hurt on the serve! And people that use poly mostly complain about tennis elbow, but my elbow never hurts at all.

Could this be due to the racquet/strings. I use 1 wilson blx six one 95 and 1 kfactor six one 95, both are strung with synthetic gut + luxilon bb alu rough 16g hybrid at 53/51. The kfactor is 78 stiffness strung and blx is 72. hurts less with blx.

I strung with full poly once (tecnifibre black code). was great but then I experienced this exact same feeling after 1 wk. I cut out the strings and switched to mfil, no more shoulder pain. But I really dont want to used full mfil and would much prefer a poly hybrid (I used a hybrid before without any problems, babolat pht with synthetic gut). Maybe its the guages? the racquet tension? the string itself? so confused!

Sorry this post started to turn into a story lol but I had a lot of questions. Basically, could my shoulder pain be due to strings and racquet, and if so, how do I still use a poly hybrid (what gauge, what tension, how do they affect softness on shoulder)

Thanks everyone!