Darkness before flipping crop?

I wouldn't use a darness period before the flip. Many people have talked about trying this in the passed and mention stress of some plants, i even overheard(read) thats certain plant din't reciver well. Some growers add more darkness time to fasten rippening resulting in lost of yeild to achive faster harvesting which can be arlright if timing is a factor. But the onky thing that i can think of if you do a dark periods before flip other then a stress is elongation. The lack of light us going to cause the plant to stretch tremendously... The best advise for reduces stretch would be to use a bleu spectrum light during first weeks of flowering other then this. I would just flip 12/12 . And do a dark period befor harvest.