hi there,
it might be too late, but i had the same problems till i figured out that the underwire really do not plug anything at all! my midwife, with quite large breasts herself, suggested to give them a try bc they really offer supprt, and if i notice the beginnings of the plugged ducts, i can still prevent them by the normal hot shower method. you might not like this idea, but i wear 36 DD and no problems with underwires. i buy them at mimi maternity and even at target, they have some nicer onces nowadays. good luck though :)
also, i just ordered a sling on this website, does anyone know what mehod they ship with?thnks