After several buckets, I can confirm that I am hitting my 9.5 983K way straighter and just as far if not further. Hitting the sweat spot more often IS producing.
There are a few things to consider in my case.
I am 6' and have a "wingspan" of 6'5". Yes, I am still part gorilla.
My miss is a snap/duck hook. I am trying to keep my ball position off my left heel AND hold my the back of my left hand toward the target...VERY hard to do after 10 years of letting my right hand dominate the follow through.
Bottom line, it is working for me.
What did you end up using for shaft length? I am in the same boat as you (5'11 6'3 wingspan). I have a 46in now and it is way too long. Should I cut it down? If so, from what side? Or, should I get a new shaft? The drive is a Callaway Razr X Black 9.5 stiff shaft. Swing speed is 102-106 range.