Here's what Glen Seekins wrote about ring height, for his product:
"56mm obj Medium on < 5 contour (sometimes med high)
Medium high on sendero contour
High on >7 contour"
(Taken from a thread on Sniper's Hide: Ring Height Info - How to Measure Correctly - Sniper's Hide Forums
Otherwise...here's a nice equation provided by "Palmik" in the same thread:
"Here is the equation:
[rail height + ring height] - [bell diameter x 0.5]
If the value is positive, then your bell will clear the barrel. Optimally, you want that bell to be about 1/4" or less over the barrel. This will give you a tight cheek weld and provide for more precise trajectory. Be sure to account for Butler Creek caps if you intend on using them."
I would second the use of NF Ultra Lightweight rings or Seekins.