Spring-Fit Parabolic Circular Dish (prints flat)

I almost passed on to this contest until I had this idea. Pretty simple, with no special printing instructions. 

Print whatever size you want. It doesn't seem to matter. The blue/gray ones in the photo are 150%, but 100% works great too.

I made a hexagonal one first, then a circle, then a square. Let me know if anyone has any particular shape in mind, and I'll make it for you (within reason).