Originally Posted by aliasfox

I would try a taller stem (or an extra spacer, if your steerer's long enough) before trying a shorter stem. If your back feels fine with a 90mm stem, it might feel cramped with a 70mm. A buddy of mine gets hand numbness when he rides two of my bikes with ~550-560 stack, but has no problem with my bike that has a 580mm stack height. I'm fine with all three, but find myself more comfortable for long periods in the drops on the bike with the taller front end.