Tronxy X3 Upper Extrusion Endcap & Support

UPDATE 8/11/2017: A flaw was found in the model that seemed to appear when certain slicing software was used, specifically Simply3D. Thanks to [Creat3DPrints](https://www.thingiverse.com/Creat3DPrints/about) for reporting this! This also affects the [Tronxy X3 Legs Model](https://www.thingiverse.com/thing:2287823) So I am updating that also.

So my wife saw the [legs I made](http://www.thingiverse.com/thing:2287823) and asked "What about the parts on the top? and if I were going to make new