amgdjp,

I think the bike shop folks are in a much better position to evaluate which size bike will fit you better. The shoulder blade soreness could be caused by a lot of different things -- the bike size, the handlebar width, the handlebar height, stem length -- just to name a few.

I may be able to help clear up the confusion about sizing on the Trek vs. the Specialized. Trek measures bike size from the center of the bottom bracket to the top of the seat tube, most other manufacturers measure from center to center. A 51cm Trek is like another manufacturer's 49cm, which is why the 51cm Trek felt really small to you.

Does that make sense?

-- Melissa