This is a fascinating thread that is about 10 years too late for me. My story is that growing up, I used a Pro Staff Classic 6.1 95 and I always thought that tighter was better...unfortunately I was stringing them at 65 lbs. with Forten Kevlar 15L. Unfortunately I ended up with arm problems that continue to this day. I remember at the time my dad saying I should string lower, say around 50, and thought he was nuts.
Now looking back, he wasn't that crazy after all. I'm currently using my PB10mid with MSV Hex 1.10 Black strung at 52 lbs. (Spring-Fall) and 50 lbs. (Winter). Here's the thing, using my ERT300 I found out my sweetspot ranges around the 40-44 lbs. range. I found this out just keeping track of tensions as soon as I get home along with how long I played and how many sets I played. Another crazy thing is that I can keep playing with the same strings until the bottom drops out to around 36-37 lbs. with no problem. I also don't break strings even though I hit with a good amount of spin since the strings don't really move all that much.
What I really like about my setup is the slingshot effect, people have commented that I tend to hit heavier if I just whip the PB10. I also like the ease of playing defense; just stick the racquet out and the ball just goes. Playing offense definitely is a ton better too as I'm getting a ton of jump on my shots; being lefty and having the spinny setup is definitely a boon.
Has my game changed from going to lower tensions? I think I try to exploit the setup now as it pertains to my game, with the PB10mid I can definitely hit some wicked angles and touch shots while also pounding big serves and groundies. Slightly OT, my trek-font PC600 was strung with VS17/Isospeed17 at 48/53 and it's still in the frame, but has dropped tension in the low 40s and I feel that although I'm not hitting the wicked angles, I can still reap the benefits of great defense and a more penetrating, flatter ball from the ground and serve.
The lesson learned for me is that I should keep an open mind from now on and try something new every so often. Who knows, it could be a pleasant surprise!