Fellas, please. Let's help the man mod the sprinkler, not debate on what materials he should or should not use...
Thanks everyone, I found another valve like that one and I modded it, just drillig a hole in the side, at the right height.
Yeah, I kinda forgot to mention that. You can put the hole nearly anywhere, just as long as it exhausts the pilot area.
Sometimes I use 12 g CO2 thingies and I don't even know what pressure I arrive at, my gauge is limited to 14bars.
They are called 12g powerlets, for future reference. If you wish for more detail on using CO2, check out the link in my sig.