Woody, In addition to what LJ has stated, I would make sure that you have a continuous vent path for air movement from your soffit to the ridge. The insulation has to be able to breathe. You can use the formed styrofoam vent panels and run them from the soffit to the ridge. BUT make sure they are perforated, so the fiberglass can vent into the air space. Also, if you don't already have it, you should install a continuous ridge vent in addition to the soffit vents.
In addition, I would use 6 mil plastic over the rafters after the insulation is installed to effect a better vapor barrier than kraft paper.
One other thing, you didn't state the size of your rafters. You may not be able to fit the R30 into the space available. You could fir out the rafters to make room, otherwise you may have to reduce the thickness (and R rating) of your insulation. But if all possible, I would try to stick with the R30 as LJ suggested.