Nobody has replied here, I have no idea of the product you are talking of, but from a tech's point of view who has worked on many machines; you are asking alot. I assume you are getting allsorts of banding, judders and inconsistant prints? If you had a c650X I would say change the screen to dot2 type2, it's a lot coarser but it will give an even flat halftone. You may have screen options in your engine or your application to get a similar effect. Alternativly you should try and print the grey with a 5% cyan background, you won't see it but it will give you a much smoother halftone.
