Correct way to set rear angle?

Still not sure if I am where I should be in order to have a 6-8* drop after reading pishta's explaination. I think I am where I need to be. I set the protractor on balancer and had a positive 4-5*. I then set the rear at the same positive 4-5*. Then I rotated the rear housing an additional 6-8* down. Shouldnt this be the correct setting?
Thanks
Rod