I have packed out many Elk on my back and no matter how you go about taking it out, you need a good pack. Plain and simple, spend the money on a good pack. Now before you go buy one or say to yourself "I have a good pack" it's important to remember a few things. Meat is dead weight. Most "good" packs are designed for hiker/campers that can effectively "arrange" thier pack to manage weight, etc. Test your current pack or one you might buy with this concept in mind. Fill a big bag with rice or dirt, something that acts dead and test it. Get all the weight on your hips and look for a good pack that settles everything to your hips. My personal favorites have the hip adjusts that you crank to add/release tension.

Just my 2cents from alot of trips carrying meat. Good Luck!