Right guys sorry to burst your bubble, as long as the mounting face is flat
"DON'T USE ANY LOCTITE".
The o-ring makes the seal, and it is designed to seal the face at up to 900psi, and i have taken them to 4000psi without a hint of a leak. If you doubt the strength of o-rings, look at what seals your hpa tank to the reg, a simple o-ring, nothing more.
I have used an angel air coupled to an lcd through these fittings, which were only done up hand tight. No leaks all day and perfect operation.
Trust the fittings guys, they have been tested far more than anything else on your marker, except the bottle. The bottle and fittings, are produced to a set of standards, that are made with a considerable safety margin.
Enjoy the fittings guys.