i don't think you can go much wrong with silicon really nym, it's pretty tough stuff now (used to tear as soon as you looked at it!). as for rubber type, the RTV is best to go for, otherwise you're talking about heat curing, or heated peroxide curing (the latter is good if you want your nickname to change to goldilocks) which may or may not be feasable at your facility ;) hardness id say around 20-40 shore A hardness for mpc like pads, though 12-15 may do if you're after somethng more squidgey. i made some buttons with 12, and though they were a little soft to start with, they've firmed up now, and are similar to tv remote buttons. personally i'd go for slightly harder than 12 though. http://www.artmolds.com/category60.cfm