"Well, yes, you are not expected to use the whole sheet, but cut square pieces for corners and experiment with different sizes. Too small and APM will be floating too much and the flight will be unstable, too big and it will be too stiff and not damp…"
"There are special materials created for vibration dampening and better than silicone. Search for "Sorbothane sheet" on ebay or elsewhere. They are of different softness and AFAIR this doesn't mean just the weight it can handle, but also the range of…"