Sod all mate!
i run a fully eclipsed/voodoo'd impulse with upgraded valves etc and have found i get from a 1.1 2000 psi fill 3 pots and a hopper max! so in theory i would get about the same if i was to fill a 0.8 to 3k... this is with an uber efficient imp mate so i think you aren't going to have much gas to play with before you have to fill up again... up to you though..
hope this helps, RObin