Maple is a very dense wood and there's no need or way to fill them to deaden them even more, like you have to do with hollow metal stands. Any fill you use in those stands will "sound" different than each other.
What I did with my Timbernation stands was to use some Les Davis constrained layer damping pads to rest the speakers on and they made a slight improvement. I would imagine using something like Isoacoustic Gaia footers would work even better.
All the best,
Nonoise