Isolation for speakers on spikes

So folks, do you put the spikes between the speaker and the slab or under the slab? I have a pair of KEF 104/2s on fairly heavy carpet, and I use 2" hardwood slabs below the speakers, because the front heavy design -- the mid-range and high-frequency drivers are mounted in a separate enclosure that hangs on the front of the main encloure -- makes the speakers a bit unstable on carpet. I bought the KEFs used and notice that they have holes in the bottom presumably to receive spikes. I have wondered about putting spikes under the slabs to really tie things down.

db

I have the slabs resting on the carpet.Have considered putting cones under the slabs but i dont really want to lift the tweeter higher as it would be above my listening position.

Heres an interesting article:

The Sound of Surprise