Generally one should give one's primary reg (in the case of HPA almost always the tank's reg) output 200-150psi above what you want to set your secondary (inline reg in this case) reg's output.
So if you're going to set your inline reg to an output of 250-350psi you should either set or buy an hpa tank with an output of 400-500psi (minimum). Of course a normal/hp output hpa tank or co2 (room temp pressure for the co2) will work fine, as has been pointed out.
Edit: Woops, didn't see the above post. TBH I also rarely see any difference in whether that rule is low or high pressure. The exceptions to that rule are guns that shoot at high rates of fire and require low large volumes of pressure to operate (i.e. Gen E Matix, certain stock impulse models, shoebox shocker, classic valve level 10 mag with an electropneumatic trigger setup, etc. etc.). In the case of a pump cocker that doesn't run at significantly under 200psi, you probably once experience any problems. But if I were you and were in the market for a new tank or had an adjustible tank, I'd make sure to get/set it with an output of 650ish-850ish psi. That's why I love my ninja regs.
Last edited by toymachine; 11-30-2012 at 08:58 PM.