Just ran through some tests and came up with these settings - figured I would post in case it helps anyone. (Also: feel free to double-check/validate these settings!)

Lower rail: 6.2 (measured at the tip of the longer "toe," pointing inward toward the base)

Upper rail settings by lens/focal length (measured at the tripod screw mark):

Nikon 28mm f/1.8G: 9.0

Nikon 50mm f/1.8G: 5.8

Nikon 16-35mm f/4G
@16mm: 14.4
@20mm: 13.8
@24mm: 13.7
@28mm: 13.7
@35mm: 14.1

Nikon 24-120 f/4G
@24mm: 11.3
@28mm: 11.0
@35mm: 10.5
@50mm: 9.6
@70mm: 8.0
@85mm: 7.0 (?)
@120mm: 6.5 (?)