I would definitely contact Sonus Faber on this.
Most center channel speakers that I am aware of, are not just regular MTM speakers that you place on their side.
I believe there are other design differences in order for the center channel to do their job of reproducing voices. Since music is not their job, they may not be optimized for that purpose.
Dispersion is usually quite a bit different for center channel speakers, than stereo main speakers.
I am pretty sure I heard from a speaker designer, that center channel crossovers are usually designed differently than stereo speakers.
I'm just spit balling here, but I would guess they will not image as well as specifically designed stereo speakers. I would pay a lot of attention to that aspect of their reproducion.
But I too, will curious to hear what you think.