I've never had a plant "stress" on me from topping..Sure it'll have a chance of stunting the plants severely by topping a large portion, BUT that's if you wait too long to top. Wait until the 4th or 5th node appears, top the plant just above the second node. It'll take a day or two to adjust, but your plants will bounce back, if noticable stress does even show. In my opinion, lst is very time consuming and often distracting from what the plant actually needs. Tying, un-tying, moving strings, tightening strings. Each string or band or clip is just one more variable added to an already tight list of things the plant NEEDS. Topping, on the other hand, is definately a guarnatee of results...but only with one action, ONCE in the plants ENTIRE cycle. Once? No ropes and strings and clips and ties? NO. Top it once, let it grow. There are plenty of folks that are ready to neigh-say this even before i typed it out, and i can't change that view. Take my advice, avoid stress and disruption of the plant's natural growth.
happy toking
JS