Here is the recommendation from Samson Rope. Note - 1 fid equals 21 or 22 times the cord diameter. I've used 22 times in the measurements below.
REVISED - For the fixed eye bury - 2 fids or approx. 4.8 inches. The 2 1/4 fids I posted prior was the spacing between needle entry/exit marks.
REVISED - For the constrictor bury - 3 1/2 fids or approx. 8.4" inches