Not how tall should the plant be before you top it, but would it be possible to take a plant thats 16" tall (in veg) and cut it somewhere around 9"? I was given 3 plants (cheese, jorges diamonds, and celtic hash) and they are about as tall as I'd like them to finish at, but they're just veg'ing right now and I'm sure they're gonna stretch a decent amound in flower. All i REALLY need from them is a few clones (one of each to turn into a mother), but if I could get some bud from these girls while I'm at it, why not, right? Thanks!