Nitrogen will have a higher gas pressure over CO2, because it doesnt liquify at under 1000psi, but you get less gas because of this.

An 80mm bore ram with a 200mm stroke, 3L buffertank, dual 1 burket solinoid valves and a 2KG CO2 storage tank will consume around 20kg of weight and will give you plenty of flipping power with roughly 15-20 flips (Il calculate that later)