Tvad,
I'm pretty sure this VTF method would apply to any ZYX. We haven't used a Yatra but it worked for the Airy 2, Airy 3, Atmos and an unreleased model we once previewed for Mehran. None of these is as sensitive/responsive to tiny VTF changes as a UNIverse, but their the sweet zone was always just above the mistracking point.
This method also worked well with a friend's Lyra Olympos, another superbly sensitive cartridge in the UNIverse's class. It worked fairly well with our Shelter 901, a very different cartridge from any ZYX. But it isn't universal, some cartridges have a wide gap between their mistracking point and their sonic sweet zone or are less sensitive to VTF in general. Most inexpensive MM's don't have the resolution to distinguish .01g changes, or even .1g changes.
We discovered this method simply by trial and error. With so many cartridges moving on and off our tonearm the concepts eventually coalesced from all the repetition.
The reason it works is the same reason minimal anti-skating works: some suspensions are so responsive that the minimal amount of downforce AND sideforce consistent with good tracking is all that's needed. Additional external force applied to the cantilever-suspension interface just smothers responsiveness.