Join Date: Nov 2007
Location: The Land of Jersey
mics, is the 1/2" a graduated gap over six feet, or does it transition quickly? I usually take my block plane and take out the scribed material, as long as the gap is gone and you haven't visually screwed up your lines or your mating piece of crown, it should look fine. With painted material I've also run the crown out, then fastened and patch in a long tapered piece of scrap, wood filler, sand and prime, go home.
At least you care, a lot of guys will say it's not their fault your ceiling drops/raises and leave the gap, or bend the crown into place but leaving the ugly lines.
I did a really bad one just recently, black cabinets against a white ceiling. There was a huge difference on eight feet and it drove me nuts because the contrast revealed everything.