IMO and strictly my opinion.. I think the step from the 1:1 4th to the .68 5th is a bit much and could bog the rpm down too low. I think the smaller step from 1:1 4th to the .80 5th then the .63 6th is a better transition. Granted, most of us wouldn't see the use of 6th very often but would definitely use that 5th .80, .. Again, just my thoughts