Vibrapod Isolators under my speakers?

I'm just messing around and tweaking some. My KEF Reference Twos sit on about a 7" high tile ledge that also holds my other components. I have some Vibrapod Isolators that I was thinking about putting under the KEF's brass feet. Is this better (or overkill) than just having them sit on the brass feet alone? Also, they seem rock solid at loud levels. Should I skip adding any sand or shot to the plinths? The components have Vibrapod Cones underneath them BTW.

Thanks for any input.
How is the treble? I have this thing about having speakers with metal spikes and such touching tile, stone or granite. I find that this makes the bass tighter but adds a metallic quality to the high end. If I were you, I would just add some small squares (about 1/4 to 1/2" thick) of hard wood between the brass feet and the tile. See if you like the difference.
Thanks for the reply.

Things sound good on the top end IMO. I have spikes that I used to use when the speakers sat directly on the carpeted floor that I have removed. The brass feet are flat of course. I'll get some small wood pieces and try that as well as the Vibrapods. That won't be too much hassle. Mass loading the plinths will be though so I may skip that at least for now.

Thanks again.
I had my B&W CDM7SE's sitting on 12" by 12" pieces of tile, put small blocks of hardwood between the spikes and the tile and I definately believe it helped.
Has anyone thought of actualy fastening speakers to the floor, the whole idea of feet, spikes and etc is to keep the speakers casing from moving at all, only the cones'n'domes should produce any sound, if you are fortunate enough to have a concrete floor, some suitable masonry expertise should render the speakers absolutely immobile. Wooden or chipboard floors are a different problem, each situation would require its own particular 'tweak'

What about wooden floor?
I put Vibrapods under my Linn Keilidh speakers when I moved in to my new house. Wasn't thrilled with spikes on wood floors. It has been a few years, but When I did it I went back and forth between spikes on quarters (to save my floors) and the vibrapods and found the vibrapods gave a little crisper bass. MY Keilidhs have the stone plinths just for info.