Pull Copter Finger Ring: Flipped M2 Screw remix

A structural remix of the pull copter ring. I only changed two files, so you'll need to get the rest from agepbiz's pull copter finger ring model.

Flipped orientation of the M2 screw so that the threads are in contact with more plastic to reduce stripped threads. 

I'm also printing the ring rotated 90 degrees so that the circle of the ring prints continuously to increase ring strength.