In my opinion the fan leaves feed the plant so leave them alone..In Jorge Cervantes' Medical Grow Bible he says to leave fan leaves alone. The fan leaves provide the plant with energy to grow more bud, so I think if you trim the fan leaves it would stress the plant a bit and probably wouldn't increase yield. However if you are certain you wish to trim leaves do the minimum that is possible and perhaps only trim part of each leaf. I hope this was some help to you good luck with your grow