I'm currently using an Air America Unireg 320 (Stainless, 2 gauges, Takes a "male" screw-in bottle in the back). Works fine, very happy with it, but I am using a composite 4500 psi rated 92Cu bottle. The unireg states 3000psi on the side, although the input gauge reads up to 5000psi- is it a case of simply switching spring packs to enable 4500 psi input to the reg, or is it a structural issue?