Cage,

Something appears to be very strange comparing your description of how the jcm would work, compared to my actual settings. I used morphing clothes to transfer the morphs. My shorts include hip2 and lThigh and rThigh, so there are three parts with jcm. They work together and the morphs match between to three parts to create a smooth transition, so the morphs in each part match each other.
The very weird thing is that I have the jcm setting at 1.0, in other words an angle of kick ( xrot ) of 35 degrees produces a morph setting of 35 It is quite possible that I have put a wrong name into the jcm or something, the strange thing is it seems to work, by which I mean it does what I expect, albeit not 100%. I tried disconnecting the jcm and I had to dial in morph values as above to achieve the same result. It is possible the morphing clothes has only copied a tiny percentage of the morph, but I don't know why it would do that.

All very confusing to me, but at least I can post here and I'm sure someone will point out where I've made a basic error or two ;-). Failing that I will post the shorts on Sharecg, and you can all have a good laugh on me ;-)

Cheers

Ian