Magnepan 3.7's versus 20.1's?

Assuming a 'shoe-box' shape, What is the smallest room dimensions in which the 20.1's and 3.7's will work well?

Stickman,
I have 3.7's in a room that is 15.5' x 19.' The speakers are along the short wall, about 6' out from the front wall. Tweeters to the inside. What is surprising to me is that the 3.7's integrate with the room much better than the 1.6's did. I'm actually considering removing some of my room treatments. Because of the size of the speakers, I can't get more than 48" from inside edge to inside edge. My guess is that 15' is likely to be close to the minimum width for the 3.7's. I have no experience with the 20.1's

15' sounds like a solid estimate on the minimum width. Does it make sense that the 20's would require greater room space than the 3's since they are so much larger? Maybe some of our 20.1 owners can comment.

15' is fine povided you place the tweeters inside. My 3.5s performed well in my listening room with about the same width. Currently, I have the 20.1 in the same room without any problems.

I have a 20X15X9' room. Back wall opens to entrance hall of house via 8 foot wide portal so room may be "bigger" in that sense.

MG20's work well I find.

I prefer tweeters on outside and have good central imaging with msuicians hanging in space (not attached to speakers). Depending on recording I can hear sounds lateral (ie "outside") the speakers.

Speakers generally "disappear".