I made risers for the subs when I got them. I had to make them high enough to be used as end tables.
The top of the sub is 25" high and that puts the center of the tweeter at 36". I sit at a distance of 8.25'. This puts my ears off axis in the vertical plane by 1.15 degrees. I do not think that this difference will be noticeable. The center is about 4" lower that the mains and I did not notice an audible difference with the speaker level or tipped back slightly.
Here is a pic that shows my front setup:
Attachment 1044