Hi Moose Mustard. I did exactly the thing you are asking about.
Firstly, I turned the spring tension adjuster back to have the rest sitting on the shelf. I then fitted a slightly longer bolt in place of the top travel stop screw, attched some suitable material,( i used serving material ), to the bolt then attached a small spring to the end of the material, then more material from the other end of the spring to one of the cables lower down. I fitted a brass crimp-on nock locater on the cable and tied the material just below that.
This is how Clint Freeman set up his Bernadini rest when he was using that.
My set up didnt work because i later found out that my cams were out of timing, but the rest worked just fine.
It took me about 15 minutes to set up at a very low cost, no more than $5.