I didn't mean thicker on yours !
To illustrate, here: http://www.aaastateofplay.com/jayhawk-surface-u-brackets-set-of-2/
Now as I said, because it is plastic not steel, thicker of course and even thicker at the base because of the screws.
Saves on material and time.
Anyway, it is what I did some time ago and didn't bother to publish here as it is so simple. Takes 2 minutes.