I am happy to report that apparently Surly included not only the incorrect levers, but the incorrect bars with my LHT build! (happy in that it is an easy fix). My fitter, who is a very tall/large man, said that such large levers would give even him problems! He was not surprised to hear that my hands were cramping at all. So he is contacting Surly to have them ship the correct bars and levers.
That doesn't mean that I won't have to focus on posture, but I knew something else had to be going on - the pain came too fast and too strong.