A leak in the roof, since repaired, caused a bedroom plasterboard ceiling to sag about 1/2" in a roughly circular area of about 18" diameter between two rafters. The ceiling has a swirled sand finish and I think it would be hard to match if we cut out the section and replaced. I am wondering nailing one or two cross pieces of 2 x 4 between the rafters directly above the sag then held a 2x2' piece of plywood against the sag and jacked it up so it's flat if it would stay. I could screw in some drywall screws to hold the plasterboard up once I remove the plywood.
Any thoughts on whether this would work or easier ways to do it. I really prefer not to refinish the entire ceiling and a contractor isn't interested in just fixing a small area. Thanks.