angled dry wall between 2x6 joist

[ruben]

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.