Yeah, it's kind of a balancing act depending on what kind of power you're looking for. For instance, if you shot string now runs 850 to 900 fps over say 40 shots (I have no idea what you gun may be doing by the way, example only) you'd probably want to set it up in the 850 to 875 fps range. You lose some power, but gain a nice flat consistent shot string that, in this example, might push your shot count up to 50 shots or more. The lower the power you're willing to accept the more shot's you'll gain. Let's say you're going for 850 fps with 10.3 JSB's. You'll need to get an accurate reading of how much air pressure is remaining in your air tube when you reach this velocity and set your regulator at that pressure or very slightly above. Anything higher and you just wasting air and losing shot count. Then you need to reduce you hammer spring tension to match the now lower pressure required to open the valve. If you've been filling your gun to 3300 psi but you regulator is set at 1500 psi, that's a lot less hammer strike needed to open your valve. There's a lot of info on how to set one up by guys that can explain it much better than I can.
I will say this, if you're looking to stay at the upper end of your shot string a regulator is not going to be very practical for you, lower to mid power on your sting and you'll be a happy camper once you get it set correctly.
Hope this helps.