hey support, okay well like sensi said, most people i know start flowerin at 1 or 2 feet. But thats just cause they are trying to do things as quick as possible. I really dont believe there are any draw backs of growing a big ass plant, as long as your grow setup can handle it. Lighting is the key. It would be nearly impossible to grow a huge huge plant with flouro's as their power is all but lost after 10 inches. So to get a big ol green monster plant you would need a metal halide or hps lamp. Or good old mister sun... but depending on your area planting times may not be perfect right now. Hope i helped, peace man.