Foam cone is very important part of good trigger pad and I tried every combination of materials that you can imagine. Many people use sanding blocks but from my experience it is too soft. You know that piezo pick up vibrations of mesh head so material of cone must be hard enough to transfer all spectre of vibrations which sanding block foam just cant do (some vibrations are absorbed by soft foam-it sound little wierd to me).
I find that eva foam from this swimming floats auxiliary tool is perfect for our trigger cone:
It has perfect hardness and it's very nice for forming cone with sandpaper. My drum pads sound much better now. One more feature: it can be formed with very small top of coupe so hot spot almost disappear. How nice is that :)
Another project that I work these days are an old cymbal pads from Alesis DM5. I bought them cheap but when I opened that was surprise for me. They have groves for edge switch and places for bell piezos. Isolation system for bow/edge and bell was there too so they are same as 3zones cymbals but with only one piezo builded in them. They sold this pads as single zone cymbals but they are actually 3 zones design. So I made edge switches, installed them and it work great. I had some luck here :)
(http://www.ebay.com/itm/Alesis-cymbal-for-DM5-/271733257311
There it is, updates from my diy room. Maybe someone get an idea for his projects. Cheers.