Share 'Nailbase insulation vs. 2 layers of tuff-r with staggered seams'

We are going to be rehabbing a home in CT in which the third floor is part of the living space. We want to get the insulation level up by using either nailbase or 2 layers of 2" tuff-r with staggered seams on top of the deck. We are going to use close cell spray foam with polyisocyanurate insulation to increase insulation and stop bridging on the inside. Has anyone used nailbase over spaced wood…