Mount that 2" HPA tank under your CCI stock for a consistent shoulder point. 
 
These nylon tank rings slide over the T-stock tube and 2" OD air tank, then clamp in the middle for a secure hold. No seams or split lines to fail, just a squeeze in the center. Uses a common 10-32 x 1-1/4" SHCS and hex nut, so you don't have to add an extra tool to your bag. 
 
You will have to take the stock off your marker to slide these rings over the free end. 
 
Sold in pairs with necessary hardware.