I plugged in a 5-pound weight package going from my zip in NC to a place in Ohio and the formula said no can do. So I gave up. However, per amd’s Suggestion I discovered that my small ULine boxes do indeed fit into a flat rate padded mailer. Now I just have to figure out what to do with my medium-sized ULine boxes.Kari, You used the word "qualify" on regional rates. I don't think there is a qualification (other than weight on each type of box). I think you have to check each location/weight with your package. I live in Arkansas and ship using regional rate to a customer in New York, Michigan and Arizona but use flat rate to a customer in Wyoming and Maine.