Tricopter DT750 Motor Mount (for 15mm square tubes)

This is an untested prototype motor mount designed at the polite request of another Thingiverse member. It was designed to fit over a 15mm carbon square tube. But since I do not have any of this square tube to test the mount on, if anyone wants to provide feedback on the fit, I am willing to make some adjustments.

Enjoy!

Update 5/13/16: Added 3mm hole with countersunk portion (6mm head) and hex nut keeper portion (6.35mm point-to-point diameter). I have not tested the fit yet, so some feed