It would be ideal if you could do some experimentation with the location of your MLP and the front left and right.
You could do as bman says and place the M5s to the outside of your screen but that will only leave you with about 5" from the vertical center of the M5 to each side wall. That will reduce lateral reflections that give a greater sense of depth and width to the presentation. On the other hand, it will allow you to sit further away with the acoustical optimum likely being about 11 or 12 feet away.
If you place the M5s behind the screen, 8 feet apart, that will leave about 2.5 feet to each side wall. Soundstage depth and width will increase but now you also have to sit about 8 or 9 feet away.
Regardless of which you choose, it is going to sound awesome!
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