I have never heard of there being any advantage to having grommets above center, but I can't see a reason to argue against that. I can tell you where the grommets are located on my snares, though. Of the 9 snares I currently have, only the Supraphonic and modern Black Beauty have grommets located above center due to the bead being around the center. The grommet on the Radio King is actually a little below center.
I also have a custom 5.5x14 on which the grommet is located just above the collar of the bottom head due to the badge not having a hole and an inlay in the shell in the panel on the opposite side of the drum. This is a stave shell snare and sounds really good...nice, warm pop and loud, crisp rimshots.
That being said, I think you could place it wherever you want and the drum will sound fine. That's my :2Cents:.
Lynn