I use one of those used tire shops in Suffolk county that look like the Flat Fix places you'll find in Brooklyn
They have mounted 15", 16" & 18" Tires and Slicks on 5 different vehicles of mine with rims up to 12" wide on numerous numerous ocassions and not once have they put a scratch on a one. Plus you get to sit on a chair like 2 feet away from him as he does it
Middle Country Rd in Selden, if your interested I would gladly go there with you on a weekend day
Did another set for me two weeks ago amof, 18x10 Rims w/ 29x12 ET Streets