Hi Andrew,
Fantastic! Very happy that my settings helped. I found that when I started using SGP's auto focus with my Edge that I couldn't get near 2.5 - 3x the HFR when out of focus, compared to at focus. Step sizes that big would put me in donut land, and at that point, the auto focus routine became unreliable. With the latest improvements to the auto focus, I found that I was able to increase the step size and get closer to that 2.5 - 3x ratio without any problems. The improvements to the auto focus routine seem to make a big difference in donut land. It is easy enough to increase the step size for a few auto focus runs to see how well it works for you. If it doesn't show any improvement, then you can always go back to the settings that you have now that are working fine for you. Your setting of 300 for backlash compensation should be fine.
I also highly recommend dialling in the temperature compensation with the SGP auto focus. With that properly calibrated, you can go hours with perfect focus without having to stop and do an auto focus run.
Dean