I would recommend that you aim for about 1500-1600 psi regulator output pressure as then you can still run a 1.8K burst disc without blowing it all the time.... That will put a (stock) Disco right in the middle of the sweet spot also.... Don't forget that if your regulator has a 3K burst disc on the output side and the regulator leaks, you could end up with 3000 psi in the gun.... You will need some sort of bleed valve between the tank and the gun or you won't be able to remove the Foster from the gun with pressure in the system....Bob