Maggies a waste if only 3' from backwall?

They would still sound pretty darn good but not optimum IMO.

The extra few feet away from the wall improves the bass and gets rid of some muddiness, thickness and lumpy bass compared to what they can do.

I should also add that soundstage depth will improve if they are farther than 3' out.

of course ymmv

good luck

I have 3.6's (tried 20.1's) and they are 40" from my rear wall, and they perform very well. I would worry more about what you plan to drive them with,(don't get me wrong, placement is very important, try experimenting with different configurations). They will reward good choices when it comes to amps. 20.1's were amazing, but my 8' ceiling seemed to take away some of their magic and my incorrect equipment choice (and cables) left me wanting more. Also consider bi-amping the maggies to get rid of their x-over, that was a big step forward for my system. Hope this is helpful.

I have 1.6QRs in a 14 x 19 x 8 room with plush carpeting over hardwood floors and drywall walls. I've had to deaden the walls behind the speakers, especially the corners, to remediate excessive brightness and address slap echo. My speakers are out 5' from the back wall which is necessary for getting response down to 40hz. I also use Mye stands, which enables me to tilt the speakers forward to allow the tweeters to align in a perpendicular to my ears at my seated height. To me, getting the vertical right is much more important than the lateral sweet spot. Given the difficulty in getting them set up properly in my room, I've decided against going up to the 3.6Rs unless I can arrange an extended audition in my room. I expect the 3.6R's will be an even greater challenge in your case. I would worry that you will find the 3.6's too bright and I'm pretty sure you won't get nearly what they are capable of in the bass. You might have more luck with the 1.6's or new 1.7s. Also, they are not all that heavy even with the Myes so you could move them out for listening and back again I suppose if you placement concern is appearance driven. If you really need to go lower it might be easier to get a sub to work than the larger maggies.

Given the difficulty in getting them set up properly in my room, I've decided against going up to the 3.6Rs unless I can arrange an extended audition in my room.

That says it all in my experience. Unless you are getting a pair used and don't mind reselling them if they don't meet your expectations, an extended audition is required. I demoed a pair from a dealer for a week before deciding I could not find that "Maggie magic" I hear about.