Don't know about haircutting them, usually would LST branches to get more light distribution as opposed to cutting off energy producing parts of the plant, never grown auto either though. No worries about the sagging as long as they are perky in between watering, my sativa would be noticeably droopy a for a good 4-5 hours after a good feeding/watering, it can be expected in some grow environments I'm sure, I was using smartpots so seemed to perk up relative to the medium drying, even at 5-6 ft tall they still will occasionally droop immediately after feeding, just consider her resting/eating instead of sad =P