Love the CF barrel shroud, how far down does it extend? Just to the first support ring?
I went with a medium AAO hammer spring, changed the internal valve spring to one 50% weaker, then switched my valve to a Chinese 500cc/4500psi CF bottle* but I only fill to 3500 so don't get valve lock but get almost 100 FPS faster with 350gr bullets.
*Yes, I know these bottles are not DOT approved but filling to 3500 for a 4500 tank I think it is a good safety margin. Besides, I got a local hydro shop to test one just to see if it would pass but not mark it inspected, they wanted to know too, so curiosity won. DO NOT tighten the regular bottle mounted butt plate clamp onto a CF bottle as it may cause hoop stress failure. {Some people I know are using the DOT rated Talon Tunes 3600 psi bottle doing the same thing by the way}