We do use a 4 wheeler very often to pull animals up and/or out of the woods. We have developed a system that ties to the front of the four wheeler hooking to the front frame. from there the strap passes under the four wheeler and through an eye attached to the rear of the for wheeler.
As you are dragging or pulling the pressure of the load pulls
down on the front of the four wheeler. The strap running underneath pulls up against the skid plates and through the rear eye attached to the rear tow bar. The keeps the strap inline with the body of the 4 wheeler and will not allow it to get under or in the tires when turning.
This picture shows the rear of the 4 wheeler with the eye hanging down. The two strap passes through the eye very little pull pressure is put on the eye...
This has proved pretty handy for us...