^Agreed. If it had ever proven to help anything, we'd all know about it, and be doing it by now. Not once, have I come across anything indicating an increased yield, by trimming. Yes, I've seen results that were about the same as untrimmed plants, but never any better. IMO, your best bet, is to use some method to spread open the foliage without damaging it, during mid/late flowering. Trimming some of the lowest branches/leaves is okay, as it increases airflow. It doesn't remove any of the plants main power sources,....the fan leaves.