Those 1/72 biplanes are tiny! Good effort. I did my first rigging (1/72 esci R.E.-5) with tread as well. Unfortunatly it started to sag in the courcse of the years. I hope your rigging wil stay tought.
I later learned about other techniques such a nylon tread (not my favorite) and streched sprue (my favorite). Others use thin metal wire, EZ tread and even human hair.
Here is my build tread of a Polikarpov I-5. On page 2 there is a short explanation of how you can rig with streched sprue.