angled dry wall between 2x6 joist

I'm not sure this is a good idea to deflect but before I continue I thought I'd get some input. Here is a pic and sketch (sketch not to scale) the atic space is 4 to 7 feet high at an angle the room is 15 ft x16 feet with two walls at aprox 17 deg angle . The cieling is paralel with the floor, so will the angle drywall between the cieling joist help to deflect or am I making it worse? Thanks.