I double line with 1/2 inch rope. I start with a bowline in the wing ring, loop through the ground ring,then loop through the bowline loop. When I pull the tag end the double loops act as a block and tackle to multiply the pull force, then tie it off with a double half hitch and a quick release added to the end. I do both wings first then the tail and pull the airplane backwards to tighten all ropes. I then dial in full nose down trim so the wing doesn't lift in the wind. With 3 double 1/2 inch lines I figure I have about 6000 lbs of rope strength, or about 4200 lbs of hold down strength on a 45 degree angle on my low wing. That should keep her planted in a 80 mph breeze. Good rope is cheap compared to my bird.