Hey VDWB,
I know this is kind of an old thread, but any chance you could provide links to the thermometer and pressure gauge you used? Went to use my Spark for the first time and thermometer doesn't work. I've actually had it a few months now but hadn't had time to do any shooting due to my work schedule. I know opening it up is likely to void the warranty but I don't want to have to send it to Hatsan to get it replaced. I'm only direct filling air tubes for a Hatsan Bullboss so I don't think run time temps are gonna be an issue, but I'd rather know everything is as it should be. And I really like the fact that the thermometer you used is lit. Do my filling in the basement with less than perfect lighting. Thanks in advance for your reply.