I went through this description elsewhere in this forum, but I thought I'd place it here as well since it is more applicable here.

I used four mighty-mounts, two for each crossbar on the rack. The center bolt goes through the jack in the typical manner. I just wanted a little extra strength over the basic mighty-mount plan just in-case I got in an accident. I don't want to kill someone's kid with a flying jack. Hopefully I won't ever test it.

The picture is the view from the back. The metal plates go over and under the crossbar a little so that they might physically capture the jack if it started moving forward in a collision. Probably won't do much given the strength of the crossbars.

Anyway, here is my setup...