What you seek is here:
No, not really. What I saw once had a center of the trackball marked for proper 3"cut out in plexi, the 4 legs marked for mounting in wood like it is in the link you provided, but the trackball cut out was more in the shape of betson rather than just a gigantic square I don't want to cut that much material out.
Btw is the template for Happ trackball holder? And also I didn't mention I'm going to mount it recessed under plexi not on top of a panel
Thank you for the reply though!