I don't have the hook ends on my singletree. My traces have both the loop for the hooks or the slots for the pins to fit on sword tail ends. I don't have the proper pins & have been trying to make it work for the time being
Now that I see it again, my Meadowbrook has leather strings for just this purpose. The are tied on through a hole in the wood, go over the trace, and slip through another hole. Why don't you just tie a leather string through there? It doesn't really need much, since there is really no side force.