@redbaron no double blind study?
placebo controlled even. I think several hundred specimens would be needed.
Actually, I don't have half the experience of most of you. However in the last five years in 3 RV's I have tried Several different chemical, Thetford, Blue Power, Happy Camper, Dawn, Cascade, the geo method, etc. Now I do not poop in my tank unless absolutely necessary.
In the RVs with sensors inside the tanks, it was very difficult to keep the sensors clean and reading accurately. I found Dawn to be the most effective agent. 1/2 cup in 1/3 tank of water at the end of a month sitting, and drive 50-100 miles. The cleaned the tank nearly 100% of the time. Next trip, dump and rinse. Voila! This is the only thing that seemed to keep the tank clean. When I took the previous one back to the factory for other repairs I had them address the non functioning (dirty) sensors. When I got it back they worked perfectly. When I ask what they did, they replied Dawn and 100 miles.
Now as far as odor goes, unfortunately, my urine is pretty stinky - love that garlic, etc. I now put a few thin lines of Dawn around the bowl on occasion, and use normally. Also, I have been experimenting with spraying the bowl on occasion, (a several of per tankful, with a solution of PineSol and water (~1:8). This is my universal cleaning solution.
Sometimes I add a little Blue Power if I notice a little odor - I like the bubble gum scent. This is very seldom. The large bottle lasts several seasons.
Needing real proof of efficacy, my toilet now passes the ultimate test. Open flush valve and get real close and sniff. I am happy to report no odor. My holding tanks are dumped every 3-5 days depending on water usage.
Also, no struvite, which I did see using the chemicals.