Sorry, don't know if metric or imperial.
However, as Goatwhiskers said, not sure if you are trying to solve a problem that can be solved another way.
Normally, in shotguns, shooting high often means you are not getting your face down enough on the cheekpiece, so that you are seeing too much of the barrel. Shots will be high.
Try getting your face down more and see how it goes.
As I recall, when I first got my M97, I found it shooting high. Then I worked on getting a better cheek weld and found that it wasn't shooting high, I was. I can now take it out for informal trap and skeet and dust a lot of clay pigeons.
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