It will work with HPA, I'm not sure where I'd position the valve. Wasn't able to make the video yet. Gotta clean up the workbench, and for that matter, re-assemble my VM. I don't use a valve tool so it's kinda bad when I try to get the valve out. I'm gonna try and get one cheap before I do anything crazy, but I'll go through the internals at least.
One thing you'll need to understand is the valve is special. It's got 4 settings. The 4 holes on the back end nearest the actual Air source are adjustable. Usually meant to constrict or allow the flow of Co2 depending upon the weather. HPA will be a bit different. I haven't played with it enough to know. However, I ran mildly well on a tank of nitrox for a day. I had some hiccups, times when it leaked a bit, so I shut off the source, then filled it back up and it usually went away. Quick cycle will reveal issues.