I prefer to tripple-bag the corals. Making sure the open ends of the bags are oppisit the one it is covering. I use a couple of rubberbands to close the first two bags and use a plastic zip-tie (the kind used to bundle wirering) on the outside bag. A broken rubberband can spell disaster for the shipment. I also tape the lid to the cooler completely closed and place the cooler in a plastic bag, tied on top before adding it to the shipping box. Heat packs are great, just make sure they are the 10-12hr kind. Place them between the side of the cooler and the packing peanuts and not directly on the corals bags. Also, do not use the peanuts and disolve in water. While I am a huge fan of those for environmental reasons, you do not want a leaky or broken bag to melt the peanuts. I have had the best luck shipping FedEx Express overnight. IF possible, have the receiving party pick up the package at the local hub instead of putting it out on the truck for delivery.
Sorry...I just saw the date of this post and it seems I am a bit late to the party. Anyhoo...maybe someone else can put the tricks here to work.
Some people are like slinkies...they serve no real purpose yet can still bring a smile to your face when you push them down the stairs!:p
Have a great day! Brian