You can calibrate to a 7 stop system, 8 stop system, 9 stop system, 10 stop system, 11 stop system or how ever many you like, but by doing so you change the relationship of how much exposure adjustment equates to a one zone change.
I suggest to the OP to not be concerned with sensitometry just yet, if you intend to learn the ZS, you will eventually grasp the basics of it. That is as far as my own understanding goes, just the basics.
Rob,
You cannot change the relationship of how much exposure adjustment equates to a one zone change. This, IMO, is sensitometrically unsound to suggest so. A one zone change, either up or down, is 0.3 log exposure units on the log exposure scale. If it is up by 0.3 log E units then the exposure is "doubled" and if it is down by 0.3 log E units then exposure is "halved". That is the same relationship found from opening "up" one stop to closing "down" one stop. So, there is a "link between camera exposure and the exposure units of sensitometry" (AA). It's the beauty of the thing.
Going from Zone V to Zone VI by opening the aperture from, say, f/11 to f/8 is a one zone change "up" just as going from Zone V to Zone IV from f/11 to f/16 is a one zone change "down"; going up is "doubling" and going down is "halving". These changes are true regardless of film testing, calibration, etc...nothing you do can change how much exposure adjustment equates to a one zone change.
Illustrated this way:
Zone : Exp Units : Log E Units
0 : 1/2
I : 1 : 0.0
II : 2 : 0.3
III : 4 : 0.6
IV : 8 : 0.9
V : 16 : 1.2
VI : 32 : 1.5
VII : 64 : 1.8
VIII : 128 : 2.1
IX : 256 : 2.4
X : 512 : 2.7
From The Negative, "the exposure units have no absolute value but to express the 1:2 relationship from one exposure zone to the next".
Just food for thought.
Chuck