It will work fine with the 16 tooth spread.

1. Shimano is very conservative with their max ratings which can almost always be beated by a tooth or 2

2. Shimano came late to the compact crankset party and took the time to make a crankset that was spec'd to work with the existing Shimano derailliurs without problem. Some of the other early compact cranks worked best with a special derailleur for the 16 tooth spread.

I believe that once you have the shims that you will be good to go.