Fimming or topping would be unadvisable, any shock to the plant is more than likely gona cost you yeild. Best thing to do with autos is keep then as happy as you possibly can with a stable enviroment and just let em go for it on their own.
Remember that autos have a time limit on them so to speak, you dont have any time to play around with them in veg. They can grow over an inch a day at points easily, so if you do anything to stall that you loose alot of growth that will never be caught up on. I hear a few days LST can be good with some autos, just to let the sidebranches catch up a bit to the main cola. I'v read a few reports of people scrogging them, which I think might work because its just a form of LST.