I've tried using a regulator for velocity adjustments before on my phantom. This is another gun that isn't set up the best for adjustments, what with the set screw in the side of the bolt and down the barrel adjustment, so I put the reg on the vertical adapter with a macro line running the rear.
Plus for using this system was that it always was dialed in, always had the same velocity.
Minus for this system, first I wasn't sure that it was always given me constant velocity when I used the auto-trigger but I'm pretty sure it did, so a half plus for that;) But it didn't seem to give me the distance that I had when I was using unregulated co2. THis could have been a figment of my imagination, but I'm pretty sure of this.
All in all I will probably go back to using it, as it sucks having a $80 reg sitting around in my parts box, it does make the phantom a little heavy though, as it's a Bob Long reg, all aluminum and BIG! I could use it on my LB, but then I'd have that big heavy thing sticking off the back of my nice compact gun.