Okay - I don't know if this is helpful to others, but I've been playing around with this.

My goal:  To rig a character built in Carrara - to stay in Carrara - so I can animate and pose to my heart's content. I also want to use BVH animations to add premade movement to my figure.  Even though I've animated figures in Carrara alone, I want to take advantage of the excellent skeleton rigs from Poser figures and sometimes the animations (walk designer) available in Poser.

Method:    Build the figure in Carrara. 

Export to Poser to get the scale correct.  Compare it to an existing Poser figure so that the bones will line up - even if I need to adjust the figure (James or M3 or whatever figure I choose) so that the bone length and shape matches my Carrara figure.

Animate the adjusted Poser figure and save out a bvh file.

Import the bvh back into Carrara and it should match the Carrara figure -
Attach the skeleton and animate!

Progress:  So far I've only imported bvh and had to adjust the skeleton each time, until I adjusted my Carrara figure to match the imported bvh - but that's not my goal.  I want to have a unique shaped figure.  I want the skeleton I import to match my figure.  I think the above method will work.

I'd sure appreciate any insight.   Miss Nancy has been very helpful.

I'm still trying to add premade poses from Poser - what about a 2- frame bvh? 

Every time I try and add a bvh to an existing figure in Carrara (the caveman rigged with a previous bvh+skeleton) it just twists it up.  I have to start from scratch.  The 2-frame bvh would start at 0 position and zeroed out pose to easily mate with the Carrara figure, and the second frame would be the pose.  

I tried using poses in Carrara - but after loading 2 it wouldn't work.  Any tutorials on creating poses in Carrara? 

Never Give Up!