How far apart are the dee rings on the back of an english saddle?

My friends and I are going out to a racetrack with our horses and having a picnic lunch there. I found a lunchbox in my house with two dee rings on it, and I am going to attach some clips to it and I will clip it to my saddle. How far apart are dee rings typically on english saddles? I just need an average size, I ride in an all purpose saddle, and I just want to know. If they are too far apart I will just use baling twine and I will make other loops for it. Thanks so much in advance!