I started with that plan...but you can clearly see that there are some dimensions missing. So I bought some 1/4" foam poster board from a craft store and made some templates right on the bike...making adjustments until I got it right. Also, I changed the area around the holes...being a structural engineer, I didn't like that the holes were so close to the top edge of the plate. So I made it so that the plate was 3" wide (1/4" thick) all along and put the holes in the middle. I took the templates to a local fab shop and had them cut out and bent...total cost was about $120. Here's a pic of the hitch bracket before I got it cleaned up and painted.
