All ranges are optimised to 4cm bases, but otherwise mechanic is not overly attached to it. If you would like to play with 6cm bases it would be easiest to multiply everything by 1.5, which is quite easy as mostly 10 or 20cm are used, or for the same result make conversion 5cm to 3" (as 5cm is the smallest distance used during movement). That way everything is quite easy to measure, table size stay in affordable size and units have sufficent space to maneuvre.