That's fine. Assuming your head is not in a brace, its relationship to the tweeter will always vary a bit.
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In my room, my Sonus Faber Signums sounded poorly atop the 28" SF fixed height stands, but when I put them on 24" stands there was a great improvement in overall balance and significantly improved bass. This was surprising to me as when I owned EA I's and the variable stands they sounded great at the 28" level which I arrived at by trial and error, and never knew the height of, until a friend asked. I also had Concerto Homes and they sounded as good as they could sound on the 28" stands.
So what I'm saying is: try different heights and positions, and hear for yourself what works best. Then you will really know.