The Diff Mount clearance issue is a wierd one actually, if you measure a collection of diff to roll bar clearances there is about 3mm discrepancy between different cars. very odd indeed.

Our new mount (available here) solves the issues with every car and fits perfectly:

In fact, here is a video I made showing the flex in a standard one...

http://www.youtube.com/watch?v=4I_Yo9sS300