I use a good muslin game bag (not one of those cheese cloth things), skin it, open up the cavity, hang it over night in the bag to get a good glaze on them and they're indestructable in all but sustained high temps. Make sure they are kept in the shade. If you have to ice them use dry ice (on the bottom for cool or on the top for freezing). I've hung them for the better part of a week like this with no problem at all. The only one I ever lost was iced in a cooler.