I put mine between the two rivets and used .032. I probably used .032 because that is what I had. I looked at my plans and they didn't specify a particular size wire so I figure 032 would be large enough. Hope this helps.
Drill an .032 or larger hole between the rivets and safety it with .032 safety wire. Should take about 10 minutes (including getting the drill, etc. out) and it's easy to remove in the highly unlikely event you ever need to. Nice job on bending/fitting the hinge pin.