I've got no input to offer on the shipping aspect. I suppose ones rate to do overnight FedEx depends on volume/destination.
I have had some great experience recently however with the packing done by Brandon at FragHouse corals - small translucent cups that protect the frag, placed in a small heat sealed bag, then double bagged in the same way, then boxed in styrofoam with newspaper packing. He punches a small hole in the styrofoam lid for ventilation, then uses a hand warmer taped to the underside of the lid, over the hole, to maintain temperature. Might be common practice for all I know, but, it's an incredibly effective process.
Best of luck.