Anybody still using soft rubber isolation devices?

Would it be bad to place Navcom Silencers under the feet of a ScoutMaster wich is on a Salemander rack?

I use Isonodes to isolate my VPI Aries Scout motor from the stand.

I have 23 McCormack "Mod Squad" feet in my system, mostly under equipment or one support platform. I have another 12 or so Iso-bearings (soft ball design in Delrin cup) that support my Aesthetix Io.

No hard feet under anything except turntable stand, tape recorder stand and built in speaker spikes of the Dali Megaline.

If you look at the upgrade Grand Prix amp stands, their best footer is carbon fiber discs sitting on the floor, connected to ball socket design foot.

Yes, but not for my stereo. :)

I use Herbies Iso-cups in conjuntion with Gabon Ebony balls under my transport and preamp.
My Hydra and Dac rest on thick Maple blocks with different composite footers.
A lot depends on what component, weight, type of shelf and or material they're on.
Experimenting and proper compliance (soft, medium, hard) is the key factor in determining my sound.