Subwoofer between speakers?

After reading through a thread relating to the equipment rack between speakers, I assume that the sub between the speakers is also a no-no?

My speaker stands are 24.5" high, and my sub is 24" high, so I was thinking that the sub cabinet being below the mid-range driver might mitigate the detrimental effects to imaging. But I read a reply in the thread that I alluded to which talked about an amp between the speakers having a negative effect on imaging . . . therefore it stands to reason that a big bulky sub cabinet would be about 20 times worse.

I know that ideally I should experiment with placement . . . this is an extreme near-field listening room, and options are limited. I could get it to the outside of my right channel speaker . . . in theory, would that be better than in between?