Just have to do it carefully. I start out in 0.3 gallon airpots and then transfer them up to 3 gallon airpots.
I disagree with the previous statement that autos work better in 1 gallon vs 3 gallon. All 6 of my autos in my last grow had completely filled their rootballs into the 3 gallon airpots. I was double feeding daily. Pulled in 17 ounces off 4 autos and put the other 2 straight through dry ice.
I don't know if they would take advantage of a 5 gallon airpot's size in the time it takes for them to reach maturity, however.