This is a remix of 0athbound's Ender 3 v2 spool side mount. it was too tall and had a solid middle section. i removed a chunk of the middle, rejigged the height to fit the original Ender 3, and now it prints about 30 mins faster and weights 10g less. 

The screw holes are not the best but they do use the ender 3's original hardware for mounting, the print is inserted into the rails of the frame.