My LPR goes into the Eclipse modified front cap, but you can put it into the VFF, some people recommend it, but since the AA's and Ecstacy have them on the front cap I don't think it makes too much difference.
Whichever way still makes the VFF redundant since the optimiser/nipple type thing (not sure what they call it, looks like a solenoid optimiser) which goes into the solenoid chamber blanks off the hole in the solenoid chamber that the VFF uses to split the air and feed the solenoid. So the VFF can only feed the main air chamber which fires the ball. To feed the solenoid the air has to come through the reg.
Hope that explains things a bit, don't think I did a good job but then again I am ill