Hi all,
I've bought one of these and used it on indoor carpet for the first time last night. Firstly, the casing needed quite a bit of finishing to get it into the CR2. The casing was about 1.5mm too wide, so bolts through to motor plate didn't reach, and the brass bracket to the chassis didn't line up. I used a sanding block to take the back face of the casing down.
With the 4 gear assembly, the motor can sit further back in the car as you can now mesh onto the spur instead of an extra idler. I found this has reduced the "edgy-ness" (inventing words now
) of the front end on carpet.
I'd recommend the gearbox casing, but be aware that it's not a plug'n'play item - may need a little work first.