It is widely accepted that, if using a heavy base (such as a paver stone) for your Prusa i3, it is better to use hard feet that are able to transfer vibrations onto the mass, as opposed to the vibration-dampening stock feet.
I couldn't find any models of hard feet that were fastened with t-nuts, which seemed like the logical choice, given how you want the tightest possible coupling, so I whipped this up in OpenSCAD. Ringing test appears to show minor improvement over Y axis, and the printer seems quieter overall.
The OpenSCAD source is available for any customization needs.
You can customize the feet (for example, make them taller) by cloning the source code and playing with foot.scad
. All of the values can also be changed using the OpenSCAD Customizer.
The author hasn't provided the model origin yet.