1. Lead hose to the back
Make sure that rear part of lower receiever it's shortened:
This is how set of screws fittings looks like. In the tank fitting/top you can find adjustable screw. With the allen key you can regulate length of it and by that - you can adjust it to the PIN in your HP tank.
This is how regulator should look like after removing manometer. Sealing and nut for manometer thread is included.
2. Put hose through the bottom hole
3. Screw regulator fitting in.
4. Adjust length of the high pressure hose to the propper length.
5. Connect regulator
6. Put regulator in the stock. Lock it up with zip tie.
7. You can put one zip tie on top of the stock. By that you will make sure that you will not lose stock pad.
If you think that regulator is vissible to much, you can always go with somethig smaller: