Are you using a monitor riser with sound pads? The center channel stand I currently have has metal base and platform, but mdf legs, I plan on cutting them, as precisely as I can - to produce the slight upward angle and lower height that I need. If that doesn't work, I will build a custom stand with some wood. As shown by the measurements, the M106 has those 'eyelets' just above and below the tweeter line to be avoided.Very nice. I have done the same.
You are right in that the clarity is definitely there with a vertical center speaker. I also prefer it level-matched or else it calls attention to itself. My only issue is that the frequency response will be a little different than our L & R because we can't adjust the toe angle and will get the 0° response. We may not always prefer the 0° response.