What hight would be best to flip to 12/12

At what hight should I be flipping my plants to 12/12? Personally myself I don't think my plants are even near enough ready, but I've just read on another thread..veg until knee hight..which one of them already is..but I don't know how people can go by this method when some people are smaller than others..

You should attemp to grow them to your space. Expect them to double in size if a stabilized indica hybrid like white rhino or northern lights.

Triple in size of more sativa leaning like ghost train haze or haze.