According to the '08 catalog the subtensions at 4.5x are--
1) dot to dot= 9.65 IPHY
2) dot diameter= 1.9 IPHY
2nd focal plane reticle subtensions are inversely proportional, i.e. as power INCREASES reticle subtensions DECREASE. So since 4.5 is 32% of 14, .61 is 32% of 1.9. See how it works? It's not always perfect since power ring calibration is not always perfect, but it's usually very close, if not right on.
Just 3 days ago i used this very system with the Leupold
Varmint Hunter reticle for rangefinding an antelope, and it worked fine. My point blank range with the load i was using was 275 yds. for the avg. doe antelope at 14" back to brisket. According to the calculations if i hunted with the power ring set to 7.3x and i encountered an avg. doe antelope and needed to get a quick shot off all i had to do was bracket her between the 1st and 2nd stadia lines, and if she was as big as the gap or bigger just aim dead center and shoot. This exact scenario happened and i shot the doe at 230 yds. using the system.
The best reference u can ever have for downrange zeroing and rangefinding reticle applications are the catalogs-- Leupold
, Weaver, Burris, Sightron, Nikon, and Vortex publish all this info.