Over the last few years I've been lucky enough to pack multiple animals out of the wilderness and into my freezer. Through trial and error I've discovered hauling heavy loads is as much art as science. You need a good amount of brute strength and plenty of mental toughness, but there are a few tricks you can do to lighten that load.
1) Bring a minimum of three game bags. This will allow you the option of splitting the animal up into at least three loads.
2) If you plan on taking the elk out in three loads, keep in mind you will need to pack your camp out as well, so make one bag light enough to account for the weight of your gear. Otherwise that last hike out will kill you.
3) If you use standard breathable game bags to hang your meat, make sure and pack a couple of water proof bags, too. I use Kifaru quarter bags and contractor trash bags. For me these are as important as your traditional game bags. They keep the blood off of your gear and in a pinch you can drop them in a stream or snow bank to keep the meat from spoiling.
4) When you do the actual loading of the pack, make sure and stuff a decent amount of non-breakable gear into the bottom of the pack. This will help keep the heaviest weight centered in the middle of the pack and against your back. I use my sleeping bag and clothing for this purpose, but whatever you use, this is the most important aspect of heavy load hauling.
5) Keep all essential gear in outer pockets that are easily accessible; rain gear, jackets, headlamp, toilet paper, compass, food and anything else you may need for your long path out.
6) If you have any breakable items in your pack, keep them away from high pressure points. I made the mistake of sticking a GPS against a compression strap a few years ago. The value of that toy went from $300 to $3 in less than 4 miles.