AM8 - Metal Frame for Anet A8 - Beefed up Y motor mount for 2020 extrusion

I started printing the parts for the "AM8 - Metal Frame for Anet A8" after my acrylic frame became toast... FYI - Don't use thread lock on your screws.

I liked the idea in this variant of the frame: http://www.thingiverse.com/make:348441 which uses 2 X 2020 extrusions for the bed, this lowers the bed and gives you an additional 20mm of Z travel. But this made the motor mount too tall, and left only one hole for attaching the mount to the frame, so I made a wider one with more holes for 2020.