hey i had a similar question. you want to have CO2 when the lights are on especially during veg, and you never what to turn off your lights, if you can isolate the space it's for the better, but either way you're doing well to keep the CO2 running usually a bottle is good enough for 50 square meters, and the height doesn't really matter as the CO2 falls towards the ground anyway. you wanna get your root areas exposed, the assummption is that it will get sucked out by the fan through the leaves anyway. You'll see it will dial in your humidity aswell. If you can set them up above folks say that's better but i've never had issues setting it on the floor 🚀 good luck with that ! 🚀