Hi, Photon46. We're on the same boat. Speakers that are very tall relative to their width, like Revel F206 and Piano Ceras, can be problematic regarding isolation because of their narrow footprint, especially if on a thick, spongy carpet. The primary purpose of outriggers is to provide more lateral stability with a wider footprint. Outriggers will often provide a stable enough footprint to use Giant Fat Gliders under the Outrigger spikes, which provides perhaps the best and most thorough isolation possible. There's more latitude for other isolation approaches as well.
With extremely tall and narrow speakers, spiking securely to the floor is sometimes the only option for cabinet stability. In this case, a thin, non-squishy decoupling interface between Outrigger and speaker cabinet is about the only viable solution to obtain some degree of decoupling between speaker and floor. You don't want to use Sorbothane, rubber, or other vulcanized material that will introduce its own resonances into the vibrational environment. "Thin" Fat Dots are ideal to provide a decoupling interface and maintain speaker stability.
With most speakers on stands or platforms, the speaker-to-stand interface is most essential, especially monitor speakers on relatively tall stands. Thicker Fat Dots are usually ideal here, with more vibration absorbing and blocking "beef" than "Thin" Fat Dots. Addressing the stand-to-floor interface is additionally beneficial, of course. (With Outriggers, it's just the opposite: the stand/floor interface would be primary and the stand/speaker interface secondary or even optional.)
With speakers on Outriggers (or other base), if the speaker and base are rigidly secured with screws or bolts, the base basically functions as an extension of the speaker cabinet and isolation of the speaker can be addressed at the base/floor interface. Isolation/decoupling between the speaker and base always has potential to add additional, complementary benefit.
Herbie's Audio Lab