Need a quick answer? Majority of Defo (and pruning) to be done 1-2 weeks before flower. Defo does cause stress and it's better to stress her in Veg where she can recover quicker then in flower when she stops vegetative growth. It can stress her out much more if done in flower, but is still ok. Before flower, take whatever you feel you need too. Won't hurt her. Do so just before or after a feed so she can recover from that lite stress. In flower, you may certainly defo, but I would not go hog-wild and limit the amount of stress's I'm putting on the girls. They're not technically 'growing' anymore and can have a hard time bouncing back from any amount of stress in mid-late flower. Early flower, during stretch, they're still growing and can still recover pretty quick. If you see you missed a lot of DEFO in veg that you didn't take, you can do this within the first two weeks of flower when she is still growing/stretching and will be able to recover from the cuts.
Cheers my friend. Good luck and hit me up in PM if you feel I can help you with anything else.ππ