I was trying to figure out how to paper tune with a bare shaft without spending any money for paper or lumber to build a rack.
This is what I came up with and something along these lines might work for you too.
Basically I tied 2 cords across my supports on my back stop.
I then used clothes pins to attach a page of newspaper for the target
The newspaper is about 16" in front of the hay bales and it worked pretty good for my purposes.