Wow Howie - sitting there looking at that trio - how can you tear yourself away to watch a movie.
While I think there may be something in this tweeter height thing (or there may have been years ago) modern drivers have better vertical dispersion (a la THX?) than speakers of old. Against all the advice and theories, my system (smaller, vertical centre with tweeter below the level of the front left & right - just like yours, Howie lol) produces a pretty seamless front soundstage with no obvious dip in the middle (indeed the imaging is so natural that the 'centre' position seems to be coincident with the screen).
I've been dwelling on my dream M system lately (dreaming I wake up with a spare �20k under the mattress) and thinking, "Oh, I would have to have an HC" forgetting that I have effectively had a vertical centre for years!