The 17mm nissin master works nicely compared to the 18mm that was on there. Softer lever, better modulation for my taste. 16mm will be too soft for me so I will stick with the 17mm.
With dual 4 piston 30mm calipers:
18 mm was a 20 ratio
17 mm provides a 24 ratio
16 mm would be 28:1
30:1 - soft feel
27:1 - sweet spot
23:1 - firm feel
20:1 - wooden feel