*lol* this ones a corker... the original regulator in the n/s end of the rail has to be taken out then you put an adapter in its place. The return pipe is discounected and the rail must be plugged up where you pulled it out. The adapter runs a pipe out to the new adjustable regulator, wherever you want to mount it, either on the bulkhead, battery tray or front panel. The return pipe from the new regulator goes back and joins the return pipe going to the tank.
Basically youre just fitting the pbv remotely and bypassing the usual return flow through the rail and hooking it up directly to the return pipe back to the tank.