I'm building a platform equiped with four transducers to translate engine vibrations, flight cues, etc. from a flight sim.

The software sends out signals through a second USB soundcard which sends them to an amp and four transducers/subwoofers. The particular setup I want to recreate is called a BOSS or (Baffle Open Sub Shaker -
I'm planning on using a hoverboard configuration which means making an enclosure for each sub with a 16" tire tube. Besides these tubes, there are approx. eight 2.5" vibration isolators (duro 20 - Hudson Hi-Fi 2.5" Platinum Silicone Hemisphere Bumper) upon which the entire platform rests.

The total weight of this platform incl. me, will be about 336 lb (64 lbs for the 4 speakers, approx. 85 lbs
for a single ¾” (18mm) Birch plywood sheet, 187 lbs for me) The subs will make the platform shake at single
and double digits Hz.

The platform (approx. 4’ x 8’) is supposed to end up in a large, open layout type room, on the second floor, as close as possible to three (in this case), weightbearing walls. I am slightly worried however about the long term effects of these vibrations on the structures below me, and that isolation here, might be more critical than if I’d been able to just put the platform on the ground floor. But this is not possible for now. Also, "hoverboard suspension provides significanly more displacement and “the shaker force of each JBL is multiplied exponentially.”"

One of the users on the BOSS forum, assured me though that this probably won't be a problem because there's not enough energy to cause any damage.

Still, I'd like to see if I can further minimize any vibrations. Also, the Hudson isolators do not dampen single-digit vibrations I believe.

I have two questions:

If adding additional damping material (besides the silicone hemispheres and tubes), like rubber tiles or pads (could this somehow end up amplifying the vibrations instead of further reducing them?
There is what is called a zone of amplification and a zone of damping (zero / critical). I seem to
remember reading somewhere that this is a possibility; where too much load for a specific type of dampener
ends up with the dampener amplifying the vibrations instead.

Second question:

Should I look into a different approach altogether, using springs maybe or a combination of springs and pads instead of the silicone dampers. From wikipedia:

Springs or spring dampers Heavy loads, pumps, compressors 3 - 9 Hz
Elastomer or cork pads Large high-load applications where isolation of medium to high frequency noise and vibration is required 3 - 40 Hz, depending on size of pad and load