Is it worth mentioning that you, BRM, augmented the floor under the two speaker locations with something during the build of your room? Or am I mistaken?
Yes, but the speakers have always been on a portion of that then and now. They're pushed back to the very limits of it near the front wall.
Guys, I think these devices can help, especially if the speakers are susceptible to vibrations, etc. My Exoticas improved when I put the rubber wafers under the feet and then the nicer looking Symposiums gave the same performance. Cleaned up the mids, etc. They were also in the bad spot.
My speakers are very heavy as I have lead weights in the uppers and the plinths are 3/8 steel with heavy copper feet. But, moving my chair more than 2 feet forward and the speakers almost the same backward put me out of the nasty intersection of several room modes. No isolation feet would make that much difference and then when you have better response, there is way less need to isolate the speakers from the "room".
Remember, I made room measurements w/o the Symposiums and placed them without. Then I added the Iso units at their final spot and there was no SPL difference. It was easier to adjust the speakers around the room w/o having to also slide the Symposiums with them simultaneously.
The speakers are within a 1/4 inch of their corresponding walls Terry.