I have found with extensive co2 testing that it isn't really worth the cost when using bottled co2, propane generators are much more economical.
My ultimate ghetto solution for a grow space that size would be to tent it in your sleeping quarters and use yourself as a co2 generator ! I was sleeping with some plants (is that even legal!?
) and monitoring the co2 ppm of my room. It would go up to 2,500 - 3000ppm over night with lights on. Its reliable as you will most usually sleep in there and it guarantees amounts of 1500ppm or more (provided you have an enclosed space. I have a big gap under my door and it didnt matter. )
The rest is most definitely not worth the extra outlay for the additional gains received.
Trust me, I wanted to believe so badly, but think mild supplementation is useless unless you have absolutely terrible airflow (highly unlikely) is pointless. Spend more time improving the humidity/airflow and heat in your environment. $0.02