If hotness is possibly an issue you should definitly go for the super soft poron foam with adhesive backing, jmanword over at the vdrum forum has determined that this is the key to having pads that are not too hot. I would make it 1 3/8" high for stability though 1 1/2" is fine and use 27mm head and rim piezos. Good luck, Kurt.
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ps, take a look at superscreen, it is just as strong as pet screen only it's a third of the thickness.
Here are the cones I bought
http://cgi.ebay.ca/ws/eBayISAPI.dll?Vie ... &indexURL= which uses a 35mm piezo, has harder poron foam and has these dimensions 1 1/4" height X 1 3/8" (35mm) base diameter X 3/16" top diameter. I had to install 100k linear pots to reduce the sensitivity on my mesh heads.(diy roland style c/w roland mesh heads 10" and 12") I must say that these cones are made very well and it was easy to compensate for the hotness issue, which was relating partially to my alesis trigger io. I guess I'll see how these cones respond when I get my megadrum up and running, if I was to make my own cones I'd use the super soft stuff with 27mm piezos and I probably wouldn't need the pots.
56 input Megadrum644, Tama Iron Cobra, Taye, Sonor, Roland, Yamaha, Gibraltar, Tascam.