There are two dimensions that determine the fit - stack and reach. Notice that the difference between sizes affects the stack more than the reach. By reducing the stem length by 30mm, you've reduced the reach to the bars by more than several sizes.

Handlebar reach and brake/shift lever reach all add up. Shimano levers have a long reach. I use 80mm reach bars and SRAM or Campy levers with a shorter reach and most often a 110mm stem. Most likely, your want of a short stem is due to a lack of fitness. A too far forward saddle can also put too much weight on your hands. Some people then try to sit more upright with a shorter stem.