Using LEDR tracks

Indeed, it's the room that you work with and the design of the speakers can be very different. I usually start with your geometry and would have predicted my current* setup would have the same 'mono' affect you describe, however it does give the spread (rainbow?) across the speakers.

I noticed a couple of reviews of my MA speakers which mention 'converging just in front of the listening position.' That overcame my feeling that this looks weird!

To be fair I do get some width/surround effects with the current setup.

*This setup may change as I am adding some more treatment (bigger corner traps) and will be rerunning the LEDR process.

You are right about small changes of the toe-in angle being noticeable. I think the up/down angle or rake is also a factor, based on the speakers I've used recently.