Niksan I'm "learning" on the elf.

Thanks Surgey1972. That's the info I was looking for.
The reason I bought the bottle style Ozark was to regulate it. Unless someone makes a regulator for that specific mfg model tube style gun then generally no. As stated above contact Huma and Altaros first. It is the most reliable route.

However, given the Niksan rifles appear to use the same action IF the tube to gun interface is m18x1.5 then maybe. M18x1.5 to G1/2-14 would be needed. At that point it becomes a matter of fitting a regulator and adapter in the available space and still mounting the tube.

The inline regulators come with at least one gauge and a fill port. Which probably have to be removed and sealed. If your fill port is after the regulator then you have to leave the regulator fill port on or attached after mounting to the gun.

Generally not a simple process because there are a lot of variables that can make an external regulator installation fail on a tube style gun.

If you go that direction I would say start with a Huben Power Cricket or Blackhawk-Cricket. They are thin and reliable.

But inline regulator is a crapshoot for bottle guns, tube guns are a whole level more difficult.
 
From both a bench and a tripod if I'm in the field. You have a great idea though. I hadn't thought about a regulated tank setup. And MAN talk about having a huge plenum with that setup!
Unregulated the whole tube is the plenum.

If you were regulated the microbore hose from the tank would restrict the flow and only provide a minimal plenum volume.