I run my Desert fox deluxe on anti sypon co2(and so do 3 of my teammates) all are running the factory setup(x-chamber, 45 frame, pitched asa) and we have no problems with the reg. I can cycle my Fox so fast its been accused of being full auto, and I have no drop off. havent ever had to replace the main spring. and if you store the gun with the bolt removed from the power tube, you never need to change the power tube oring. just a couple of drops of oil in the power tube EVERY time you put a tank on it.
If run properly these guns are flawless, if a little tempature sensitive.