Magnum 360 heads "best" for my build?

What's the formula for figuring the difference in lift on 1.6 and 1.65 rockers? Doesn't seem like the extra .05 in ratio would raise the lift by .020".

If you don't know the lobe lift you have to find it
Valve lift / 1.5 = lobe lift

With that just multiply the lobe lift by the rocker ratio
Lobe lift x rocker ratio = valve lift w new rocker ratio

Seems simle enough, I'm sure someone else will chime in if I overlooked something