M3 upside down as a center? Does anyone use that configuration?

Yup.

Been running that way for a few years now.

In my situation; on top of the TV, it gets the tweet closer to the screen and closer to the same height as the tweets on the mains.

The picture falls off faster to the sides than the sound, so we all cluster together in front of the TV anyway!

If there IS an up-down lobing problem, I haven't found it!!

I too, though, would be interested in the "real truth" of the matter!

Anyone in the know!!?
Rich.