In birdman's video, Wicked sent shims to use with his bumper if needed. I don't recall if he needed them or not. One of my bumper mounts was bent from my fender bender and that's probably the reason I need to shim it. But, with custom fabrication each bumper may be slightly different.
I didn't get shims with my order, but I emailed Wicked and they are sending me some along with some other parts that were delayed.