A friend of mine (the author of "When All Plans Fail", a survival book not a remodeling book) used experts but they were just going to cut the drywall to let in the granite where the wall wasn't straight. Another friend , a high end carpenter (one of the Ranneklev Brothers of NY), said the granite should have been scribed and cut to fit the wall. He said the drywall would be unsupported where the granite was to be let in. The solution was that he added wood to support the cut drywall edges so they couldn't bow. I don't know who was right or wrong so don't shoot the messenger.
Debt free almost forever!