Hi irregularshed,
I agree that there are some really helpful and fascinating threads here 
As for you question on foam, when I delved a bit deeper I found that key are first mass, second spring stiffness (as they determine the natural frequency) and then damping while of giving sufficient movement capability to ensure that the energy is not just passed through.
For an ideal isolator, mass, stiffness and damping would need to be tuned which can either be done by measurement and calculation or by trial and error. My very simple tutorial part linked above supports in particular trial-and-error.
However, it is perfectly feasible to just use what you have and experiment a little until you are satisfied.
You could for example just use the 12mm foam and stack two sheets above each other to try to find a compromise between movement, spring stiffness and damping until you are satisfied. You could also cut foam into four smaller patches and use them as individual feet with your paver. That increases contact pressure and changes spring stiffness (non-linear in this case) and damping.
You could also use this to try to turn a vibration isolator into a true vibration absorber like seen in my tutorial with an additional board of wood. I have tried that with my parts and it does indeed absorb vibrations at the cost of increasing overall height. However, foam is not a good solution for that as it needs tuning of the spring stiffnesses.
Best wishes and 
Eno