Paul, I didnt want to say this in Kodys tournament but Nitrogen is not filled on weight but on pressure. So 2x 1,5kg Nitrogen makes no sense. Under FRA rules (and I hope you guys use those pneumatic rules because the RFL rules are lethal, Im amazed no one died there yet) the main bottles are only allowed a maximum of 1000psi.

CO2 is liquid inside the bottles, and therefore those are weighed since pressure is too variable.