Keep topping every couple weeks until you see pistils wait another week or so and top again. figure out what your max finished height can be and keep you plants half of that. If you still get a little too tall just bend and tie down the branches.Every strain will be different so its best to start with genetics you know or have solid info on. Every strain will be different and react different to topping/bending.
Keep them in good sunlight if possible, not too much shade, and then bend them over and tie when they get about a foot high, you ll get a few main stalks that you have to stake up, but youll also get a few colas on each plant.