LST advice! I keep snapping tops

Hi mate, it is really up to you and how you want her trained. The idea of LST is to use all the grow space. Plants don't always grow in a square shape canopy to they have to be trained to do so. It creates a larger canopy of top bud sites to form. Using topping technique is also helpful while training. The problem is you are growing autos, which by design hate stress. Topping is a great technique to increase buds sites but LST can shock her, resulting in lower yields. I don't see an issue using LST on autos, you just have to get it done quickly as they have such a short veg stage. Get 90% of your training done before veg stage ends. Or, just top them and let them grow. You may get better results. I hope this helps, good luck and happy growing