The gap can be adjusted slightly (1/2 inch) when you have the factory hitch installed. Remove the plastic panels in the spare wheel well and you will see the 4 bolts and metal plate that was added when the hitch was installed. You only need to loosen 2 bolts on each side (i forget which 2), but you will then notice that the bumper can be moved around slightly. Move bumper slightly and have someone hold it in the correct position and retighten the bolts.
The instructions in the hitch install don't seem to note this adjustment, but if you do a DIY on the hitch, you will see what I'm talking about.
Good luck.