Martin Logan on it's side for center channel ??

No. I am sure that will not work well. The floor stander was made to stand.

+1. I had a floor stander that matched my L and R speakers so they all matched as a center channel for years. Try it that way and see if you like it. That is how they do it in the studios, matching L-C-R.

Those dedicated CC speakers are only shaped like that for people that stick it under a TV.

. That is how they do it in the studios, matching L-C-R.

Yeah, but it depends on the height of the screen. 

has anyone tried this , or just going by how traditional floorstanders react on their side ? Logans don't have 4 or 5 drivers in a line , just 1 panel for mids and highs

Okay. I do currently run my old 1996 Martin Logan SL3 electrostatic hybrid loudspeakers with cone woofers on their sides (woofers outside), and a ML Cinema center channel in between. They sound great with all three tilted up about 20 degrees or so. My screen is 11.5 ft wide and the room is 12. No room to stand.

The panels are charged so I'm not sure why they must be in any particular position physically, aside from being positioned properly for the audience. This set up doesn't bounce off walls and ceilings either (or way behind you) and has worked rather well for years now. It's a front wall of clean powerful sound through good amps.

Hi OP:

The thing about a traditional ESL is that they are designed for wide horizontal dispersion + narrow vertical. If you turn the speaker around 90 degrees you’ll get a whole different story. Now you’ll be narrow horizontal and wide vertical. That’s just with the ESL panel. My point to this is, what makes an ESL sound great vertically hurts you horizontally.

The woofer (or woofer + passive radiator?) was clearly meant to be reinforced by the floor. Also, this will look weird. :D

I mean, sure if you have a 3rd ESL and want to do it just cause then do it just cause. If it were my system I would not expect it to be that great, so why bother wiht an ESL in the middle to begin with?

You should notice that the center channels ML makes are short (left to right) and augmented by a tweeter for a reason.l