I tried flex guards that snap on but found that they don't really protect the carbon from crashes, but only help against light scratches.
I remixed the model I used because it fit the arm perfectly.
These are the changes made to the original:
- Removed snap-on part to allow the model to slide from the bottom
- Added extra material at the end to act as a bumper
- Added support for motors with hole distance of 19mm
- Added features to allow securing with zip-ties.
After a few hard crashes I can comfortably say that they protect the arms much better.
I suggest that you use good quality zip-ties so that they don't break too easily and need replacement.
I think that PETG works better for this than PLA, but PLA should also do a decent job as well.
Enjoy your flight.