in a perfect world, yes. i like to look at the pressures to make sure the charge is ok. humidity and temp, along with actual bottle temp, play into it. honestly, 2.9 lbs is too much for a 240, i know that what the label says. i've found by watching things and dialing back the charge .1-.3 makes for good cooling. it's all observation, what's the pressure, what's the inside temp? .5 or so at a time above 1.0 lbs, the less at a time at 2 lbs. takes longer, but then i hate flat rate. and yeah, the rear ports are a pita 240 or 740. good luck, chuck.