Conditioning attic – GreenBuildingAdvisor

Currently remodeling a home in climate zone 6 with a living space in the attic. The interior is gutted down to the studs. The home just had a brand new metal roof put in before I took ownership. The home has gable vents and a ridge vent, no soffit vents. 

I want to close off the vents and condition the space without having to add r25 of CI on top of the sheathing as I want to avoid disturbing the brand new roof. I have furred out the 2×6 rafters to 2×8 to create a level surface for Sheetrock and allow for additional insulation. I do not want to lose any more headroom in the living space by adding CI below the rafters. Is it feasible for me to do 2” of rigid foam in between the rafter bays pressed up against the sheathing (to allow for removal or repair of sheathing in the future) and then fill the rest of the cavity with closed cell spray foam along with any minor gaps not filled with the rigid foam? 

The space will have central air with adequate returns.