Although the height is where you want it, the foundation your speakers rest on isn't inert enough in my opinion. Isolation can't be achieved by use of foam and speakers to the degree necessary to isolate your speakers, not to mention the coupling needed.
From what I understand, the base should be firm enough as to not allow vibrations to travel up to the speakers and the speakers should be coupled to the base in such a way as to add another degree of isolation and to help drain vibrations from the speaker itself.
Foam and speakers just won't cut it. Microscopic though it may be, the amount of vibration that foam and speakers allow should be enough to smear or veil the sound to a degree that should be detectable in comparison to a really inert stand.
All of this will sound fanatical, but that's what this hobby is about. :-)
All the best,