Print the 5 and 8 mm sides in PLA, ABS, your mom... some sort of rigid plastic. I recommend at least 6-8 walls, 25-35% infill, since you'll be tapping the screw holes (M3 tap, or slit a screw and drive it in there).
Print the spider from TPU, ninjaflex, etc. You can experiment with wall thickness and infill to change the stiffness of that piece.
I've included sldprt files just in case you want to modify or molest my design. :)
Enjoy. Let me know if anything is screwy with the tolerances, and I might fix it.