Ok, I have a story to share on shoulder pain, and the possible help of physical therapy:
25 years ago, I broke my collar bone, and it healed with an overlapping lump. I was a very active cyclist at the time, but after the injury, suffered shoulder pain. It actually got to the point that riding would cause my shoulder and elbow to buckle. I stopped riding, for that reason and others, and favored that shoulder for 20 years.
Four years ago, I started riding again, on flat bar bikes. I learned that if I had my wrist turned palm down, as it is on flat bars or the tops of drops, I could ride forever, but if I turned my palm parallel to the ground, as it would be on hoods or drops, or even bar ends, after about 15 minutes, my shoulder would buckle. So it led me to doing 130 and 150 mile rides on a flat bar, perfectly comfortably, but couldn't go 10 miles on a drop bar bike.
Then two years ago, I hurt my shoulder at work, and my arm was useless. I ended up in physical therapy, and in five sessions, not only corrected the arm injury, but addressed the twenty year old shoulder issues. I do not remember the name of the muscle, but basically I had a weak muscle that runs below the lower portion of the shoulder blade, everything else was stronger, and my shoulder was essentially pulled out of position all the time. Those sessions, and the resulting exercises, have gotten me away from flat bars, and into drops.
Didn't mean to be long winded, just wanted to say that I played with fit and farted around with drop bars to work something out, but I never would have gotten there without the physical therapy and addressing a simple issue that I didn't know about.
And I also have to say that anyone who says flat bars are always uncomfortable is full of poo, but that is a different story.
