The standard Polypanel is designed to rotate about 270 degrees -- from as close together as you can get them to 90 degrees "backwards" to form a right angle.
For my application, I wanted to create a structural support in the form of a truss that would be completely flat, i.e., I wanted the polypanels to not be able to bend at all in the "backwards" direction.
In order to stay together under load, I found that I had to reinforce the polypanel connection with cable ties, so I added small internal triangle at each corner to guide the cable-tie placement between the Polypanels and also for attaching the whole polypanel structure to the object to be reinforced.
The picture shows the application for which I designed the polypanels. I have a "grill gazebo" with a soft roof that makes it much easier for me use my grill when the weather isn't cooperating. Unfortunately, the soft roof distorts under load and forms large puddles. To eliminate this, I made a truss with one-way polypanels to keep the roof flat.
So far, I have partial success. The truss (pictured) has reduced the size of the puddling, but I'm going to need more to keep the entire roof flat and eliminate the puddle completely. My printer is running as I type. Now, if only there were a contest to win a 2nd 3D printer so that I could double my output... :-)
Note: for this application I printed the panels at 200% scale.