Okay, thanks! It occurred to me that the fix could be made to the raw bvh file if that's simpler than scripting for Poser.

I do already use some very useful scripts by Ockham and Phil C, but this transfer of data from one body part to a different body part in just this way seems not to be out there (unless I misunderstand how some of these can work). Ockham's "Copier" is similar to what I need, in that you can copy a range of frames to another body part, but it seems to work better on like parts (like, Left Hand to Right Hand) and not to different body parts, plus I don't think it blends the frames.

Thanks for considering looking into this!

--Tim