The sled is the answer, not only saving your back, it makes carrying equipment a breeze. The sled pulls quite easily.
I have seen a few variations of how to go about building one.
This is what I came up with.
It simple to build, and doesn`t cost an arm and a leg. I decided to go with metal tubing. I heard of too many stories of the plastic tubing cracking or breaking.
Along with the ease of putting it together, with nothing to glue, the added weight was worth it.

1. A 4` plastic sled
2. pre-bent 68`` x 3/4`` metal tubing with a threaded coupler on the angled ends.
3. A 2`` coupler to attach the pipes together.
4. About 12` of 1/4`` nylon rope drill holes evenly spaced all the way around the side edges, thread the rope like a snake thru these. can hook onto bungees easily.
5. A scrap piece of plywood for the nose. gives the sled a little more durability for attaching the pipes to.
6. Three 1/4`` eyebolts to go thru the front of the sled.great for hooking bungee cords to.
7. Four half moon couplers to hold the pipes to the plywood. bolt these thru (no screws)
8. Two 1/4`` x 4`` eyebolts , one for each end of the pipes. place the eye facing each other on the inside side the pipes about 2`` from the end..
9. 4 carabiners , to hook to your backpack and the eye bolts of the sled