I've always grown in small pots with the "hefty autos in small places" idea....I've been changing my grow pots from mostly plastic 2-3 ltr to the 1 gal air pot due to ease of handling. Seems plants are healthier too. Learning to fill properly is the first thing...
When I transplant my double solo cup seedling, I make sure the cut outs of the solo cup are below the medium level and the medium is above the top holes of the airpot. The solo cup forms a type of funnel which aids in minimizing feed/water mining out the side. If the airpot is packed properly, you'll have little issue.
I get mine from amazon...bout 15 bucks each.