The DP spur gear didn't fit well at all for me. It wouldn't seat all the way down until I dremel'd of the bottoms on either side of the spur. If you put in a different pinion you will have to dremel for that too. The thing that broke it for me was that there was not a longer screw included for the ball that the body clip goes in at the back and there wasn't a slot machined in the top of the cover like there was in the top brace to keep the ball in one position. So if I wanted to use the DP cover I couldn't use the body clip in the rear.
Good concept, half-way implementation. I learned.