On Sun, 26 Aug 2012 08:21:45 -0700, Jeff Liebermann wrote:

BTW, WHAT is the purpose of the bottom brace anyway?

Some of the larger J mounts have additional support arms like this:
http://sadoun.com/Sat/Products/Winegard/superDmount-6.jpg
Looks like you have the mount, but not the arms.

Oh. That makes sense.

There's NOTHING about that in the instructions!
They just say to mount that bracket below the antenna. That's it.