Mini Kossel doubled frame top vertex - for 1515 extrusion

I built a larger version of the Mini Kossel and found the frame would wiggle a bit when printing fast. The bottom corner mounts were already nice and tall because they also held the stepper motors but the top corner pieces were pretty small and had only one mounting bolt on the vertical extrusion. So I customized the original frame_top part to create a doubled size part and still have space under it for the end stop switch mount.