This was originally made for a laser cutter, so the parts were understandably pretty 2D. Then someone made it for a 3D printer, but it was still pretty 2D.
I added a little 3D to the upper body.
I also added some clearance so the parts would go together easier. Mine holds together, but you may need some glue.
The zip file has the Solidworks files in it.
Pretty much print and play.