I did a minor update to the file:
https://drive.google.com/open?id=0B-...jVVeDB1SkhONEU
The only thing that's changed is the weld nut slot is a little wider. This way if you don't want to use, or can't get a weld nut you can use a 1/4x20 nut and just grind down a washer a little bit.
Photo_-_Google_Photos.jpg