Thanks for taking the time to place a comment @akadashultraflex
The Strong & Flexible material that is provided by Shapeways, is really really very flexible. It will not break, so feel free to force it even more!
So far I have broken only one of my cases (iPhone 4) when I kept using it myself daily for more than 2 years. Furthermore, I believe that it broke because of its thinner design and not because of the material itself.