Hopefully, it's just specific to me. String is so personal in what people like as well as how it effects their arms/shoulders.
I'm getting pl2 put in today so we'll be able to see.
I've never had any arm problems at all and I've used all the toxic high stiffness strings: I used to love BBO at 58 with no side effects so go figure.
At any point were you approached by a man in a poncho offering peyote?