I just mounted ours and the gaps are there. The only option I've ever seen that looked half decent was to put a backer behind it but I didn't want to mess with it.
I picked up a cheap, plain black tag on amazon to use as a backer on Jen's JK. Just make sure you're running all the screws as the tag (obviously) won't reach all the way to the end of the holder and engage the tabs.
--Ian