No I have not, and I completely understand where your coming from. You hit the nail on the head, I'm a "no pic no proof" kinda guy! I wasn't for one second stating that Co2 will NOT benefit plants, I'm just saying with all this time in effort going into this yeast sugar concoction has anyone tested the actual benefit ppm wise? Saying simply it will help the plants isn't satisfying to me, I'm a solid number kinda guy. I feel like most of the growers who use this sugar yeast method are small scale ops that have so much variance between cycles that saying they noticed an improvement could be caused by a number of variables. If someone could give me a solid number that would definitely put my mind at ease and hell I'd probably go make my own. Even in my case, if I added this concoction to my op it would be hard to tell a noticeable difference because although growing does take a miniscule amount of skill it takes a majority of experience. My next batch is always better then the one before it because I, just like all other growers, refine their methods and techniques to apply to your next batch of plants. So saying their was an improvement over your last batch doesn't tell me much because your next batch should ALWAYS be better then your last.
Are you 61? Anyway, Kool. Like my dad used to always say (he was an Artist & Teacher) "An Artist is 3% Talent and 97% practice". You hit on some valid and important points which I missed. Esp. the fact that our next grow automatically should have a difference (hope 4 the better!) from the previous, if just for the tiny experience, and so on. Practice makes perfection. Unfortunately, I learn from the school of hard knocks.
So, as far as CO2 goes, so many factors, most overlooked, contribute to success. A simple closet grow and the brewery concoction is an excellent way to experiment and find out if one even has the discipline to manage this small set-up. Believe me, the larger the footprint and more advanced CO2 generation, the larger the problems, BUT the larger the gains (like penny stock v. 3 digit). At the least, the "concoction" helps mask smells if this be an issue. I have thought of using it solely for this purpose (x-tra wouldn't hurt). So cheap and E-Z. If visitors have to happen, one can always say "I'm makin' my own wine, did you know you can brew XX gallons legally?" and onwards to the next topic. Plausible and out of sight... I tried and grew up with all the different methods I could find and arrived at where I'm at (LP gen. +/-15 cu ft/hr using automatic Atmospheric controls Blooming area 1450 ft3) after necessity.I learned an awful lot, hopefully without too much waste and expense. I believe, from my heart of hearts, that it is worthwhile. BUT then it will only be as successful as the commitment one gives to it, as well as their performance and dedication. AND if one addresses all the issues to 100% perfection, then will one have a chance. Weakest link rule applies here, big-time. Simple air infiltration and leakage are the worst enemy's. It is hard to completely be air-tight. You'll know you are when you have difficulty opening/closing the door. Elevating the level to 1500 PPM isn't difficult (with capable equipment), keeping it there w/o heat issues is another. It takes a lot of trial and error to get the air thing worked out. I have to tweak it all the time and it is in my daily must verify list right after all the plants and equipment have been dealt with.
I don't think I have ever seen anyone actually document a grow with and without CO2. It would be very interesting. Until someone does this, everyone is going to remain the same way that they are.
Again a diatribe, sorry...