I sling my bass so that it is the same height standing as when I am sitting. Never had one problem with my fretting hand, but on my plucking side I get some "stiffness" in my shoulder, sometimes a little pinching in the elbow. I think it is because I have long arms and in order to have good form with my plucking hand I have move my shoulder back while I am playing. I have tried lowering my bass but then i have issues with the fretting hand and end up tilting the bass like an upright to get down to business. I have always played with my thumb anchored and I know it may be because of that so i am working on floating. Any other ideas? Am I just a wimp? I just realized that I have never had any adverse effects from this other than a little discomfort while I play and a tired shoulder afterwards. My bands rehearsals can go into marathon mode and last 6 or 7 hours. The next day I am usually ok. maybe a little stiff.