Regarding the outriggers and spikes, I prefer the sound of my 2.4s with them on. It might simply be, however, that the improvement I hear is more related to having the speakers elevated another 2-3” rather than any coupling to the floor. My floor is tile over slab. The spikes sit on thin wood pieces to protect the Oriental rug I inherited from my parents. Anyhow, I’ve noticed I prefer the sound even more if I sit in a chair lower than my couch and another ~20” closer to the speakers. But this is changing more than one variable at a time, so can’t really say to what degree the lower listening axis makes it sound “better”.
Regardless, my modded Thiels sound superb. I hope Tom is able to bring his upgrade kits to market soon!