Cone/Spike Decoupling Gliders are ideal for use between the stock Songtower spikes and floor. If the spikes are uneven and you're not able to adjust, replacing the spikes with Threaded Stud Gliders would be perfect; you'll have the superb isolation/decoupling, easy mobility of the speakers, plus individual height adjustability.
(With superb isolation/decoupling with Herbie's dBNeutralizer-based loudspeaker isolation products, there's often no real need for spikes at all. Little Fat Gliders or Giant Fat Gliders can be used in place of spikes altogether.)
Herbie's Audio Lab