One of my first and favorite improvements I made to my OpenPPG last summer was quick latches for the arms. They automatically click lock when the arms are folded out and quick release with one finger to fold the arms back in. At the top of this thread you can see the original ones I made out of Lexan. I decided to test a 3D printed version which would make it available to more people. They simply pop rivet into holes that are already in the frame. I printed them with PETG and they work great!
Here is the file:
Arm Quick Latch.stl (170.8 KB)