Pinching and bending the main stem until the inner tissue crushes, without breaking the skin, is the quickest way to stop a sativa that is about to hit the light in week three of flower. The bent section heals into a knuckle within days and the plant redirects growth into the side branches. A written breakdown of supercropping on https://hazesativaseeds.com shows how much pressure thin sativa stems take before they snap. Do it on the softer upper growth, the woody lower stem will just crack.
