Got this done today, used the black plastic retainer thing, rear (closer to firewall) where I broke the plastic part out and just ran two fender washers to hold it in place. Used spray paint inside the bumper to locate, did a small hole to let the ball poke through the plastic to verify centering, then masking tape and step bit for the big hole. Went well, but need to spend a lot of time dialing it in.
Also, since this setup is a bit further forward and doesn't control the rear tip as well, I came up with the idea of using a relatively thin but stiff piece of metal and some double sided tape or glue to control the angle. I've not done this yet, but plan on it (if it's even needed).