jm,
I have only started hanging, so I don’t know if I will be of any use, but here goes anyway.
All my hanging thus far has been SO with the wench with only light weight so far (5 lbs). I find it very comfortable (I’m hanging right now!) and have no problems.
However, In Australia, I can’t seem to find the clamps you guys use so I had to improvise. I use a cut down handi-clamp (By Irwin). Rather than using it as Piratesteve illustrated in the alternatives thread, I have cut the gripping “pads” off the clamp as well as about 1/8 of an inch behind that and my shaft is now clamped by the inner edge of the “arms” of the clamp, making for an oval shaped clamping motion as required.
This way I have a clamp that clamps both side of my shaft just as the clamps you guys use does. The only difference is that because it is not hinged at the bottom like the cable clamps, there is clear space both underneath and on top of my shaft. Maybe this makes all the difference? I guess it would because I have zero pressure underneath from the clamp. Maybe you could try a handi-clamp?