Hi Pete,
Here is a link to a site that you may like to look at to help get your scope aligned. HTH.
Also, if you have a good repeatable digital focuser, you can run 4 focus runs on each corner of the chip (on the same star by moving the scope) to see where best focus is. from the results, you can asses if one side of your chip is further back from best focus from the other side of your chip (assessing tilt).
CS
Josh