No, no, no! You want the size that allows three passes of the cable, not two! See my lame diagram above. With this setup, the cable cannot come completely out of the ferrule. The cable could slip and become loose in flight, but it will not fail completely. I have both A3, 4, and 5 ferrules in my shop for various size cables. Cable size is dependent on the size of the model and it's anticipated flight loads.

John