The bigger the charger pulley the more belt wrap contact on the pulley but also less charger rpm with a larger pulley, so IMO you will have less slippage with a larger pulley. Since you have less belt wrap contact on smaller pullies and thereby more charger rpm as you go down in pulley size you would likely have more slippage as you reduce charger pulley size and as a result increase charger rpm.

Agree with white01ss - makes a lot of sense that the way to adjust tightness on an RPM belt is different than the Green HD belts.