the sooner you flower the smaller the plant. Also less plant material to make buds. It's a balancing act. You can use LST, supercropping, or a scrog to keep the plant lower to the medium. I use bushmaster to control my plants stretch, but have heard some people burning their plants with it. Also, using MH light untill the plants stop stretching will keep the stretch down. Another thing is to keep the light as close as possible to the plants to keep the stretch down. That's about all i Know on keeping them short.