agreed. theres no reason to waste perfectly good tires, so props for using them up first. i hate being wasteful! the difference between 255/35/18 an 255/40/17 is a couple hundred dollars, hence why i run 17" wheels (and lighter weight too).
Just for reference i am lowered on yellows, running 17x8.5 with 255s with roll/pull in the rear and absolutely nothing done to the fronts and i NEVER rub! and it even looks "aggressive", if your into that
. So it can easily be done, you just have to have proper fitment