You asked about a 9 oz. CO2 tanks and then mentioned you want to do an HPA build.... I was merely pointing out that CO2 tanks are not safe at 3000 psi (which is the typical pressure for HPA tanks).... The 2240 was never designed to have the tube pressurized.... When you change it to either a bulk fill CO2 or to HPA use, you have to seal the valve into the tube and anchor it against the end force generated by the pressure.... The QB79 tank block has a design flaw for HPA use in that the screws supplied with it are very soft (easy fix, get better screws) and they are WAY too close to the end of the tube.... I know of one that blew off the end of a gun when the regulator failed and the gun was pressurized to 2600 psi.... That means that the design is marginal even for CO2 use in high temperatures and lacks a good safety margin.... At a MINIMUM, if you are using a 2240 tube and a QB79 tank block you MUST protect the gun with a 1.8K burst disc on the output side of the regulator.... That will limit you to about 1500-1600 psi maximum or you risk blowing the disc.... Even so, it is a good idea to add two more screws to secure the QB79 tank block to the tube.... JDS Airman sells them already drilled and tapped for 4 screws.... I would recommend a Disco valve and mounting screws in close fitting holes in the tube so that all 3 screws take equal load.... Obviously it is also important to drill the screws holes for the tank block accurately as well....Bob