Ride height on my car will be determined by a combination of factors.
Air pressure, operating range of the 'bags, clearance for the wheels, etc will all have to be taken into account, and the ride height will be determined from there and the alignment set at that point.
Being as my car is still in the project phase, and not currently driving, I haven't yet determined what or where the optimal ride height will be just yet.
Just spitballing here, but if I had to guess, I would say I expect to have 3-4" of ground clearance at my lowest point (which is my driver's side header as well) under normal driving conditions.
It's been a while, but if I recall correctly, the pics from under the car were taken with the car aired up, or at ride height, I don't recall anymore. If they were taken at ride height, I'd estimate there's probably 4-5" of clearance to the header (you can just make it out in the background).
Donovan