I have always made it clear that the Stomper is not a precision instrument. It can't be when the plunger is a hollow plastic tube. In order to make it a precision instrument, all of the components would need to be made from solid materials and moved in a mechanical method such as a screw drive. While this would be a great solution, it would add more than $200 to the cost. Anyone is welcome to design and sell one of these solutions and it has been discussed many times - even on this forum. I have no intention of making it myself because it would be hard to develop and too expensive to sell. The Stomper is a brain-dead, low cost, simple solution that gives great results if you pay attention to the centering which is simple and fast to do.
Using the Stomper requires you to perform the final centering by feel and by eye. I have had no problem in using the thumb and middle finger of both hands to feel when a ring is centered on the the ring below it and visually inspect the glue lines to make sure that the joints are aligned when the bowl is rotated 90 degrees three times before the glue sets.
What the Stomper does is that it prevents the rings from sliding after you put clamping pressure (weight) on the rings and that is the problem that segmenters have had throughout time. It also lets you add a complete row of open segments at a time with precise spacing instead of the one-segment-at-a-time if you use a lathe mounted jig which both ties up your lathe and dramatically increases the time it takes to make an open segment bowl.
I have also found a shift in the setting of the rings. It is so small that it makes no difference in the final product. My suggestion, if it bothers you, is to adjust by hand the ring prior to putting pressure on it. Then check it again. That being said I have found that the "Stomper" is by far the best method of centering the rings with the least amount of effort (yes I am a bit on the lazy side)!
I found an adapter at the big box store that screwed into the bottom of the housing, I believe it is to attach the water line to the housing. It had a half inch hole through it. I then took a length of half inch dowel rod and drove it through the adapter and into the bottom of the plunger part. This stiffened it up considerably when the vessel gets taller. There is still a small element of touch needed, along with visually checking the alignment.