Bogie, it's generally suggested that at least 3" of breathing space for rear ports be allowed. Because of the size of the compartments, as Ken noted, you should have no problem with that factor, especially since you should have the front of the M22s protruding a little bit, say 1", from the cabinet to minimize diffraction effects. Also, the M22s should be tilted slightly downward so that the tweeters point at your ear level at your listening position. So, not ideal, but it works.

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Enjoy the music, not the equipment.