Is my room OK for Magneplanar 3.6's

your pushing it with the size of that room .Maggies need to breathe.Your room might work but again pushing..good luck

I have my Magnepan 3.6s in the end of a 11 ft wide room, with the speakers about 3 ft from the baack wall, and only about 20" edge from side walls, with the tweeter inside (rather than outside edge)
I sit about midway into the room so the speakers are 7 ft from me seated position. Great.
One thing you might also try with a square room is a diagonal setup, so the room is a diamond in relation to your speakers and your seat.

I agree with Schipo

Try setting up the speakers using the 1/3 rule. If the length is 15' place the speakers 4' from front wall sit at 10' and leave 5' behind you.Changing any of these by a foot worked for me . This was learned from robert harleys "the complete guide to hifi" has worked wonders with my mags.If these are your first mags also place diffusers behind the speakers and listening position as well.And if you add a subwoofer place it right by your listening position.This setup of a subwoofer blends best usually.