Here is my solution to how i did a working ragtop. Im sure there are better methods out there, and i am always looking for thinner materials......but this works for me.
First of all...or course....cut the hole the size you want.
Then......take some evergreen strip and glue around all the edges......leaving some over hanging the edge a little bit........to make a track for the sliding ribs/bows/rods........inside and out.
The material i used was the kind you find in physical therapy/rehab places for doing excercises. The color i used was the blue....its the thinnest (the color dictates the "strength" of the rubber, or thickness).
I then covered the rubber with masking tape to give it a textured vinyl look. I also did this to hide the glue marks.........when you glue to rubber, it has a tendency to draw up on the opposite side. I then colored the tape with a Sharpie marker.
Then i just use either.....rods or flat stock (in this case).........to slide back and forth in the channel you made around the opening. You can make as many folds as you want depending on the size of the opening and how many rods you use.
Also, i find it easier to lay the masking tape on the rubber BEFORE you cut so you will get straight edges without stretching it. And instead of having the top overlap the channels a little bit, i cut the rubber to the exact size of the opening.
Here is an example i did on a truck with a sliding ragtop.
Here is the ragtop with the channels painted black.


You can see the channels it slides in real good here.
