I bought a R10 without rotator to use with a Nikon 10.5 mm lens last fall. I shot mostly with the lens rolled with 6 shots around which provided lots of overlap. I tried 4 around in portrait which gives almost zero overlap (or small gaps) at the horizon. 4 around rolled worked with a large sawtooth at the bottom. So I think 5 stops would be a compromise. Why do rotators skip the odd stops like 5 and 7?

So I am trying to decide between the R-D4 and R-D8. The R-D8 needs the adapter and is slightly larger but I can skip every second stop set at 10 to give 5. The R-D4 is slightly smaller but doesn't list an install kit for the R10 (none needed?). Does the difference between 62 and 54 mm diameter make any real difference?

Any advice?