Hi Alex,
I'm at a similar stage to you in that I want to correct for tilt with my ZWO 2600mc but haven't been sure how to go about it.
A few days ago I stumbled across this thread on Cloudy Nights:
https://www.cloudynights.com/topic/8...cussion-astap/ which discusses using the program Astap to quantify tilt & adjust for it. I'm still new to using Astap but have analysed a couple of my images using it and it looks like a way forward. The thread is extremely long however but hopefully it's of some use to you.
A good idea might be labelling the adjustment screws and keeping a log of your changes so you can back them out if they go the wrong way & make things worse. With your RASA being such a fast focal ratio it would be particularly sensitive to tilt.
Hopefully others with more experience doing this might chime in.