As a running change I put the aluminium shaft in my second build. I don't really have an issue with the steel one in the first car but wanted to give it a try. I'll put one in the first car too one day.

Space and tolerances are tight in this chassis (a big difference to most other cars, like the Vorza I was used to) so it's surprising that this wobble issue wold exist. There is not much wiggle room against that shaft in places.