I’ve noticed that the x-motion seems to be smoother in one direction than the other.
This manifests as smooth X lines in one direction, but “steppy” in the other.
Almost like the difference between the stepper motor pushing vs pulling.
I see the belt bouncing more in one direction than the other.
Is it possible that this is down to belt tension?
OK answering my own post…
Yes tightening the X belt smoothed things out, as can be seen in this photo:
https://picasaweb.google.com/lh/photo/AMHnkzXSNpqjNhgJF3qz7mFJdVthYMqWer3aYtk5XeE?feat=email
Still work to do on the bridge settings as it’s still a bit like spaghetti 
Sorry two threads with same info…
But as a quick summary yes I am using these settings, so now rope bridge rather than spaghetti