just saw this, since the 07 bumbers are more "squarish" the westin bull bar will push in the bottom a lil bit. what i did was make a half circle into the bottom, and the bumper returns to its orignal spot. BTW: u cant even tell that the half circles are there because the bar will cover it all up. heres some pics of mine for ya,
here is a perfect picture describing what happens. u can see my lower valence turns up and in.
These are after my tires and lights, but u can kinda see that the bumper came back down to normal position.