I used 3 methods with results within .001 of each other.

1) straightedge across the face with digital calipers measuring between the bottom of the bore and the edge

2) same straightedge across the bore, but used the depth probe on the bottom and subtracted the thickness of the edge

3) Inserted the race, and used the straightedge across the cover mounting surface and used feelers to measure the gap between the race and surface, then measured down from the edge to the mating surface, subtracted the gap between the race and the edge, and that told me how much of the cup was ABOVE the mating surface. subtract 1/2 of the race OD, and that gave me the C/L distance above the surface.

These are $300 Fowler certified/calibrated digital calipers, not some cheapie set.

My inaccuracy comes from measuring down to the pinion face. My straightedge won't quite span the case directly over the pinion. I can just barely catch the edge of the machined face, so I may be .001 or .002 off.