I use an older model 17" Stubben Parzival dressage model on my mare (she's 14.1hh). The banana shaped panels won't fit a flatter backed horse properly though (you actually want the full panel to make contact with the horse's back to have proper fit and weight-bearing); it really depends on your mare's conformation what shape panel she needs.
Stubben has a saddle fitting video that is new on their homepage. Keith goes into detail as to the reasons you do not want full contact.
I have Genesis D and Genesis Special D's that I can measure today as it is slower in the barn since it is Sunday.
FWIW - quite a few of our horses are extremely intolerant of loin pressure, so these saddles have been a godsend and the key to moving up easily from 4th-Intermediare. They are so strong in their back (back movers too), it is the only way to stay in balance with their gaits and not interfere.
mbm - we do have 2 older model tristans and there is much more contact, but the saddles are tolerated by the horses better than other manufacturers for whatever reason. I find them to be too hard to ride multiple horses but the balance is fine and it is sufficient to work one horse in a pinch.
My 16.2 h TB had 16" between his last rib and 3 fingers behind the shoulder. Yes, he had a very short back!
Stubben Tristan and Genesis both worked for him, both in a 17" seat. I can't even begin to explain to you how awesome and free he felt in the stubbens. I tried a whole bunch of short backed/ upswept paneled saddles on him, and these were the right ones.