We do, it's the little white dot in the video at 0:40 in. Managing the internal growler PSI has been my highest priority throughout the development process. During transportation growlers frequently go above 9 psi as a result of warming up and jostling. I have tested failure rates with growlers and have never had one fail below 100 psi. The average is around 112.
There has been some concern about the height. I've been keeping mine in the door of my fridge so height hasn't been an issue for me. After some discussion we've decided that we won’t be making any changes that increase the height of the TapIt Cap.
It can use either a 12 or 16 gram cartridge that can be threaded or unthreaded. The number of growlers per beer varies based on a number of factors including beer type, but the main factor is temperature. I get between 8-10 growlers per 16 gram cartridge.
At this time, the TapIt Cap does not adapt to different sized growlers. I picked the current threaded version because it is the most widely used. I have every intention of manufacturing TapIt Caps that can fit other growler types and after the rewards have been filled we will begin producing them.