I use a leash for my bigger birds, literally it's a training leash for big dogs ...it's about 16' long, and doubled over for this application gives me about a comfortable 6' to 7' of leeway from what I tie too. Our field has a run-up area, but the rope/leash seems shorter then I'm comfy with, and the leash I use is 10 times stronger then what the field has available at this time.
I wrap leash around a pole near run-up area(never in the pits please), and then loop around tail of plane. It seems the only way it will come off is to remove from tail of plane. I know the pole is definately not coming out of ground, and that just leaves tail of plane. I seriously doubt tail of plane is coming off either. I do use the fusalage also to distribute the load. If one of my buddies is available, I will get someone to at least be on stand by, and I won't run them alone at the field, for safety sake. I've learned this habit from here, and have heard of to many mishaps that are just that. You just never know.