I'll check this week, because it seems that 75% of racers at my track run MTX-4s. Just about every 0.8 centax I've seen mount the tranny gears with the 3mm screws instead of being solely keyed in place with the gear holder and an c-clip. Considering the power clutch can be used on a MTX-3, it should work.
Gear mesh was a bit off, which signaled an end to 2nd gear. A pain, but not the end of the world. I gotta work on the clutch timing. Not sure if I want it to hit late or early. Tranny shift point is spot on, though
Didn't think about the CNC vs the steel thing. If I had, I wouldn't have ordered another one for that diff! Oh well. Since the track is big and flowing, maybe I will make that diff a solid and throw it in the rear when traction goes up (as it does at that track). I went with the J. Lin setup they had online and it seems to work just fine for my driving style