We started using 14" pallets on our manual this year. I wish I'd tried is a long time ago. Since these accommodate all the way down to a standard Youth Small tee, we rarely change pallets anymore. (Just for sleeves, & other special locations.)
Bonus tip: We use 23x31 screens, and we blockout the edges w/ emulsion - no tape. With squeegees matched to pallet size, there's very little ink mess getting on the frames. Deinking & cleanup is a lot easier, and the elimination of tape has greatly improved setup & teardown times.