I was not aware that the Q45 had a similar front suspension to the old 240SX. It indeed looks like that arm would allow some caster adjustment, but it also does look a bit over-extended as you have it set. There should be machined notches on both threaded ends that indicate maximum extension, and they should be just showing out from the turnbuckle (NOT the jam nuts!) at the arms maximum length. This preserves about one diameter worth of thread engagement, which is the normal rule for our products. (18mm dia in this case should have a minimum of 18mm of thread engaged in the turnbuckle.

At this time, we don’t have a plan to make a proper length arm for your car. I surfed our prints a bit to see if we have a longer sleeve you could use and came up empty also. Turns out that arm has the longest sleeve already. I also didn’t find either end that would work better.

The thread is M18 x 1.5, but unfortunately, the flattened end that would be easy to reproduce longer is left hand thread, not normal RH.

Check your engagement and see what you have. If you have nearly 18mm, you probably have enough. If not, you might want to consider other options… That’s not a part you want separating on you.