Gravity works because one of the active ingredients is placo, it is a plant growth regulator (pgr) and is approved for ornimental plants, do your research on it before using, it is also used as a pestcide and gloves are recomended when working with it, it will be absorbed through skin. If you do use this type of pgr (gravity, phospoload, moab, bud blood, dr nodes, ect) you can use at about 10 days into 12/12 and just about all stretch will halt great for super stetchy plants) and you'll see a lot of cotton balls start, once more at 14 days and those cotton balls will get much larger, then again around the end of week 5 to begining of week 6, you'll get some big hard nugs for sure, use at 1/4 -1/2 strenght, the first time I'd stay 1/4 or less at most, too much is not better.
IMO it will effect the end products flavor, but this is.something that is not major, it is possible that it can be carcinigenic, but there are no studies on its use on a smoke plant product, guess they dont use on tobacco.
Just make sure to do some research, I used to use, was taught a commercial recipe that called for its use, similar to above, and I didn't know any better and didn't understand what it was... I used to stir my nutrients with my hand/arm once in a while not thinking about it, read up on it and used heavy rubber gloves from that point on when I used it... I avoid using it for most part, but if I really needed to make sure a crop was above average in weight I'd consider it, I'm not so sure I believe all the harm warnings (but thats just me based on MY research) due to the combustion rather than ingestion factor and it is approved for use on apple and some fruit trees.