I know this doesn't directly address your question, but here is a photo from a previous thread on measuring backlash. The "tool" was configured from common stuff found in the shop. It might give some ideas on different ways to do the measurement or to make up a tool. Typically the measurement is done after other adjustments, and the CV flange is out of the transmission.
http://forums.pelicanparts.com/uploads7/IMG_1873+Copy1145228336.jpg
The photo is in this thread:
http://forums.pelicanparts.com/showthread.php?threadid=274915