pinching makes my plants grow faster and they seem healthier as a result of the stress.
and i pinch every branch multiple times, it never slows down growth or hurts my plant.
This is what Subcool says about topping slowing plant growth.
"Topping is an area that is misunderstood by many growers. While a single growing shoot will produce a larger single cola, topping a plant properly can put 4 colas in the sweet spot of light intensity. This allows more of the plant, especially the lower buds, to receive better light and produce larger buds. The overall yield of the plant is greater than an un-topped plant in most cases.
Its important to top the plants early to get a good start on this style. As soon as my clones have rooted well and have started to grow I chop out the meristem, causing the plant to divide into 2 growing shots.
This will slow the growth down initially but in the long run you will have a stronger plant that yields more. If this is performed low enough, the plant will actually develop 4 heads - just leave 4 growing shoots.
Not all strains benefit from topping, but most do. Some really short, slow Indicas like Urkle just take too long to grow out when topped like this, but this method allows us to harvest 5 ounces consistently in soil per plant. To be more clear: all plants do better if topped, but some slow-growing varieties will require additional time to mature to a proper budding plant size."
http://www.cannabisculture.com/v2/content/subcools-topping-tips