Hey, Brian, welcome aboard. Regarding the heavy pellets and springs, if your gun has a stock spring in it, pellets over about 9 gr. can and probably will shorten spring life, sometimes radically. Aftermarket springs with wire of .128" dia. or larger are probably okay. That said, all my guns, one of which is/was a CFX (gave it to my brother), did best with mid-weight pellets, around 8.5 gr. My HW 77 actually seems to prefer them even a little lighter, around 8 gr. With my CFX, I got best velocity and power with JSB Exacts and RWS Superdomes, both 8.3 or so.
How has your CFX been? Mine ate 2 springs before I converted it to a gas ram. Both springs went about 2500 shots, the stock spring broke, and the replacement JM Tarantula spring collapsed. And no, I wasn't feeding it a diet of heavy pellets.
Anyway, glad you found your way here, lots of good people and info. Enjoy!
Dave