I printed with basic PLA, 15% infill, on a relatively fast speed, on my MK4. I had no issues, and they have been on my wall for a few days now! 

*Make sure to fasten to wall by hand*

There is two different designs, the 'normal' has the same curvature and screw size, but also a 'bigger hole' design. The screw hole on the smaller one is approximately 3mm and the bigger screw hole is approximately 5mm.