I've tried full gut in stiffer racquets that are 65+ flex and it still bothered my arm, while I can put full poly in my 58 flex racquet and not have any issues.
Having tinkered with every possible string type and hybrid, over the span of multiple frames with varying string patterns and stiffnesses, I have found that racquet stiffness and weight are going to affect arm health more noticeably than string type. Changing string type has more effect on ball trajectory and ball feel.
Just my 2c
Head Pro Tour 280/630, MP 18x20. Tour Bite 18/Mosquito Bite.
Sampras serve, Agassi backhand and Federer forehand. heh heh