Insulation, Radiant and Vapor Barriers - Insulating 2x6 rafters in finished attic

I'm finishing my attic. I have 2X6 rafters in which I'll need to insulate. I understand I need to put in baffles to allow for air flow. What is the maximum R value insulation I will be able to put in the 5 1/2" deep cavity combined with the baffles. My thinking was put in: baffles->r-19 unfaced insulation then cover it with Reflectix foil. Is that a good plan, or should I consider R30? Does the Reflectix provide the vapor barrier as well or am I totally missing the point?

I've also heard of people adding furring strips to increase the cavity depth, but space is limited as it is, so, I'd rather not do that.

dealing with 5 1/2" doesn't provide a lot of insulation. baffels or a one inch air gap won't move a lot of air, but going with that only leaves you 4 1/2", or about r=15 for fiberglass. Going with solid polyisocyanurate at r=7 per inch will give you about r=31, getting closer. Add another inch across the inside before the drywall and you cover some of the thermal bridging and add another 5 to the count.

Here is a link to read for additional considerations:
Welcome To Home Energy Magazine Online (http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/95/950309.html)

Bud