Well, I made the switch today. Pulled one of the AIM 5 speakers out of the ceiling (back channel). So, have abandoned my surround sound setup (for now).
The AIM 5 speaker now hangs under the TV and points directly at our viewing seats. Dialog sound is much better. The AIM 5 speakers are also much more "efficient" than the AIM 7 speaker mounted in the ceiling. The volume from the Yamaha RX-A750 receiver can now be set much lower. Dialogue is crisper.
Funny how this AIM 5 speaker as a center channel is much better than two other center channel speakers I have tried.
I know, not the ideal solution, but, it is working for me. I just need to figure out what type of enclosure to make or to just wrap the speaker in black speaker cloth to hide the guts in the back.