ahh i use to have an eclipse shocker like that, memories.
I used to run an impy on co2, works fine performance wise, but you do get your arm stuck to your bottle
I would advise shelling out a bit more for an air system, as if you progress in the sport then you can attach your air to a higher level marker, which you cant do with a co2 (for most new markers), and even if your intention is to leave the sport after a short period or just play walk ons, an air system will be much easier to sell on, and worth a lot more.
Peace
Matt