Yep as you know you were doing it wrong. Your slip will be just abit higher then that because of tire growth. MT tires will grow about 1" according to MT.

IMO, you your vert is ideal when the 60 fts are inline with the MPH for its ET.

But theres more to it then that. Some verts will have more torque multiplication then others. Most of the Good names should be in the same range of multiplication IMO. But maybe not. Congrats on your 9,s.