Those cooper's carb drops work great. Every time without fail. 11.2-16oz are fine with 1 drop. 22oz=650.54ml,so you might have to go with 2 carb drops. I know my cooper's PET bottles,at 740ml=25.16oz,& use 2 drops. Average gravity beers take 3 weeks minimum to age/carbonate nicely,but 4-7 weeks can be really good in that regard,but the flavors start to change too at 5 weeks+,as I've found.
Everything works if ya let it-Roady(meatloaf)