Modeled after: Anet A8 Spool Holder / Adapter (51/52 mm diameter) (thing:1888486) In fusion 360. I filleted the edges for a nicer look and the inside fillet means it can hold a filament spool with inside diameter from - 50-70mm

8-22-2018: Added a frame mount, modeled after: Anet A8 spool holder for 8mm screw (thing:1862701) I added support between the frame and diagonal holder. I also refined the edges with some filleting.