After months of dealing with cramps every time I picked up my mando, and after trying every left hand position adjustment I could think of, I finally decided my problem must be at least partially the result of my setup.
Even though the bridge was adjusted all the way down, the action still seemed too high, so I took it off and sanded it down last night, then adjusted the truss rod, and I'm amazed at the difference. The action can be set really low on a mando! My hand doesn't get nearly so fatigued, now.
The adjustments did change the tone a little, but it's a trade off I can live with. Should have done this months ago.