That must really piss those guys off lol.

I have an 18 in my MT2 but it might be getting a big block(see my other thread), then the rally would get the 18.

My issue is that I drive the rally either on grassy fields/smooth dirt. OR most of the time, it goes over some open but rough land in our pasture. Seeing as how the car is going full speed and hitting some small and some large jumps and landing at odd angles sometimes, I tend to break a few shafts either a the pinhole, or right in the middle fo the shaft.
I have the diff cups modded, I have some fuel line in the diff cups, and I have a fair bit of fuel line on the shock rods to limit movement.

I can't think of any RCs that would have that length of shaft that would be thicker/stronger.
Might have to try a quick home Heat treatment to see if that strengthens them any. I do have a kiln in one of the old farm buildings. might have to find it.

I could try and fabricate some, but making the ball end to fit into the cups would be tricky.