Summary

I modified this so the servo mount utilizes two locknuts at the bottom, and it's tapered near to top for clearance in some builds.
At the bottom, where it mounts into the lower link holder, there's another spot where locknuts can be integrated into the part.
I found it best to slightly warm up the piece and press in the locknuts. If your printer is like mine, the hex holes won't come out perfectly hexular but the locknut should still fit.

I had to re-print this once. After literally many hours of rather careless 4WS, dual motor variable under/overdrive hooning, jumping, crawling, climbing, crashing, flipping and otherwise cavalier driving, the piece finally broke, and that may have only been because I over-tightened the top bolt/nut to try to eliminate some slop from my upper links.

I don't know why there seem to be two different AR44 axles, but if you have the one with the non-removable link mounts, and the gussets on top, this is the one you want.
You're going to need a 38mm long bolt to get through the top holes... but the other two are just a little longer than normal