ADDENDUM:

I had to enter the Setup room one more time to delete LF2's extra body part bones to make V4 shoes fit.

LF2 with her many extra bones isn't really the best testing mule for this type of modification.

The closer the rigging is to the target figure, the less work is needed.

But all in all, I don't think this isn't too bad for a couple hours work.  :-)