I often hear that if you have too long & low a position you can get back pain, but I never hear whether too short a stem can cause the same. I occasionally get back pain while riding (doesn't happen with every ride, maybe 1/3 or 1/2 the time). I'm riding a size 54 cross bike with a -7 degree 100 mm stem that is slammed. I am 5'-11" (180 cm) and very flexible, as I can place my palms on the ground with straight legs without warming up. I don't have the budget right now for a professional bike fit, and am wondering if it's worth it to try to swap out stems for something with a greater degree of drop & longer, maybe 110 or 120 mm. What do you guys think?