I would imagine that the cable tension on stabilator cables would be fairly critical. Using a proper cable tensiometer would be my first choice. And cables tend to stretch a bit after initial tensioning when new, and should be checked a few times after installation, and obviously, on each annual Condition Inspection.
I also think that there must be a method of using a "fish scale" to deflect a control cable a known distance and mathematically come up with the cable tension. Surely there must be a formula, but I have no idea what that formula might be.
If you know the distance between the two end points, and the force required to deflect the cable a certain distance, you might have the answer.