@harpo75 I concur that placement is super important with the 8b's. I never got to your level of perfection in terms of placement. I had them out 76 in. from front wall with quite a lot of toe in. And I was never quite satisfied with the soundstage. But I believe if I had persisted, I'd get there as there are many of you who have achieved it.
I now use the 8c's and with slight toe-in the speakers disappear. The recording venue is palpable. Mind you, I am still fiddling with it, but I can now appreciate what you mean.
@rotarius If the panels were visibly rattling, then you would hear dullness. The panels handle the mid-range and the ribbon tweeters the high frequencies only. They do not receive low frequency signals. If they rattle with bass heavy music, then it must be the physical connection with the woofer enclosure that is the problem. If you read earlier posts by @harpo75 , he has installed stiffeners to reinforce the swaying of the panels not to correct a mistake but to enhance the stability of the sound field, a project that is on my bucket list.