Brian, yes what you describe will work very well.When you say the o-ring nearest the valve, I assume you mean the valve on the tank and not the one in the air tube.
The obvious choice is to add a couple screws between the o-rings, but since I had previously drilled out the tank block to get more volume in the QB79 mode, drilling any holes between the o-rings was not possible as the wall thickness was only about .160”. I didn’t have an extra tank block, so what I did worked out well for me.Troy
Was kind of new at this back when I put those together...wasn't a lot of information back then. Were I to do them all over again, would likely NOT use a Qb79 tube's screw location. Considering I run them slower (for more shots) with 850psi air, not too worried about the cut QB78.