Hi!
I am also an SCT owner and know what you mean with image shift when shifting focus orientation. However, if you use Linear mode, the risk for this is minimized, as the focuser does not shift direction (it does when moving back for the second go, but then moves forward again). Maybe more importantly: I use a Crayfoord focuser on my SCT, which removes all such issues. Much cheaper than a new scope, and you can keep the nice optical performance in the C8 Edge