I've just had to send my ga tank with a myth 4.5 reg on it back to get it fixed as it blew a burst disk on its second useI have and use a Guerrilla 68/4500 with Myth G2, but seen loads of issues with them, luckily not with mine(touch wood, I won't either), mainly dodgy Pro-burst disks leaking, there seemed to be a bad batch that instead of been flat and flush, they had a raised edge? There is a small, very thin Oring inside the reg at the bottom of a brass shaft, this for some reason can be an issue and cause leaks from a pressure release hole, either down to been dirty or in one case missing altogether!