ShadeMt, good points for sure. Packing out an elk is grueling work. Preventing spoilage is something you have to have a plan for as well.
Another option for cooling meat is to carry a coupl econtractor sized garbage bags in your pack. Load your first load of meat into your pack, and before heading for the truck, stick the remaining meat in the bags, and place is a cool creek in the shade if possible to cool the meat. If you have a creek nearby the truck, do the same withthe meat you haul down. you not only have to keep the meat at the kill site fresh until you return for it, but the load remaining at the truck needs to keep cool too.
Dark timber is a good place to hang it in the shade, in game bags. The faster you can get it cooled down the better. In warm weather, hind quarters can spoil overnight if a bull is shot in the evening and not recovered until the next day. Elk hide is some darn good insulation, and soon as that critter gets dead, that hide starts workin against you.