Challenger Antenna installation

I bought one of Metro's antennae assemblies to replace the aftermarket one on my Challenger.
I got it installed but even with the nut tightened down very tightly, the bezel is not snug on the fender, I can move it around.
That's not good as it will scratch the paint!
What am I missing here, their kit is supposed to be made up mostly of NOS original Chrysler parts. I could make up some sort of shim to go under the fender, but I am sure they didn't do that when they were originally installed on the assembly line.
Anyone else run into this problem and figure out a fix?

if you installed all parts there should be no room for movement

Thanks, that picture helped guide me toward figuring out the problem I was having.
The problem is that the bracket is loose, not retained, until the antenna is installed, and until then it wants to rotate 90° and slide down over the lower part of the antenna assembly like shown in my picture. When like that, the assembly will never tighten up enough on the fender. The bracket is supposed to sit in several notches in the lower antenna.

When the bracket is properly in its notches it will install correctly, but it was a real pain to get it to stay in place while trying to hold it in place under the fender while threading the nut from the top of the fender. A lot of time and aggravation figuring it out, and then to get it installed even after I figured it out, a little instruction sheet with a diagram included with the product would have been nice!
But alls well that ends well, it looks alot better on my car than my old aftermarket one!

glad to help
now right click save for referance