18x9" Rim advice needed

[V-max]

This is my 1st of many posts, wooohoooo......

I have a black 2006 GMC Sierra 1500 SLE 4x4 crew w/ v-max V8 & 17x7.5 stock rims & 265x70x17" tires. I just ordered 18x9" Centerline Wilderness Flint series hi-polished rims & intend to use 285x60x18 tires. I am slightly concerned that the wheels may stick out from the fender since they are 5.25" back space with a +6mm offset. My dealer said they won't void the warranty but they won't pass inspection if they stick out from the fender. They advised me to keep my old tires/rims for inspection but I wanted to sell them while still new to recoup some of the costs.

My truck came with ugly dull black wheel flares that didn't color match the onyx black & are also very "boxy" looking. I have seem them look good on a lifted long bed truck with 33" monster tires but they just didn't look good on my truck so I took them off. Centerline recommends I put the flares back on if the wheels stick out but I really don't like the flares. I have seen chrome aftermarket flares from a mail order co that appeared to be smaller & rounder but who knows how they would look in person....

The good news is Centerline is willing to cancel the order or let me return them as long as I don't install any tires on them. So my question is, has anybody used a similar sized rim & if not do you think these will stick out from the fender?
Thanks,
Doug