Any Present Magnepan 3.7i owner using them in a smaller listening space...

If you can put them against the 10 foot wall definitely go for it.

I run 3.7’s in a 13x17 room with them placed along the 13’ wall 32”-36” out and angled slightly toward seating position. Seating position is a unilateral triangle with the speakers. Electronics are on the outside with 2 rel s510’s between the speakers. Both front and back walls are treated with sound absorption. I spend hours in bliss amazed at the sound, soundstage and clarity. Have listened to systems at dealers costing north of 6 figures and, to my ears, don’t think I would do an even swap. Good listening.

My room dimensions are VERY similar to yours with the rear of the room (behind the listening position) open to the next level - which helps and I have 3.7i's. Maggies are fine to be placed closer to the outer walls than traditional speakers as they do not create the first reflection on the side walls to the extent most speakers do. It took some fine tuning to get it all right, but the sound stage created by my setup extends behind the rear wall and beyond the left and right walls. (see my system profile) I was originally going to purchase 1.7i’s but went for it and never have regretted it for one instant! Friends who are audio enthusiasts have given me positive reviews for the fabulous sound - and they would be honest with me if it wasn’t.

I owned Magnepan 3.7s (later upgraded to 3.7i's) for a number of years.  Initially, they replaced B&W 804s - I had moved and was now living in a townhouse with a truly cavernous space, and the 804s simply pooped out.  The Maggies filled that space extremely well.  Then, I moved again, and my primary listening space was quite different - relatively narrow and deep, with 9 foot ceilings instead of 12 foot.  The Maggies took up a LOT of space, and getting them correctly positioned was just not possible.  I replaced them first with KEF LS50s - they are great for a nearfield environment, but could not project well into the depth of the room.  I tried the 804s again - not bad, but still not there.  Then, having heard these produce fantastic sound at a dealer, I bought Wilson Sabrinas on close out when they intro'd the X.  It took me awhile to position them correctly - they are extremely sensitive to set-up - but I am now getting the kind of sound in that room that I would expect.  It still isn't perfect -this room is a bear - but it is fairly good.

Speaker and room compatibility are extremely important, something that I had to learn via trial and error.