I’m installing Accu-Vent baffles in a new construction home and have a few questions concerning installation details. Background: Climate Zone 4A, 8” raised heel trusses, 4.5:12 pitch roof with flat ceilings (although a small portion of the house has a 2:12 vaulted ceiling), R-60 cellulose on the ceiling. I am foaming the edges of the Accu-Vent to the trusses to minimize any air leakage up to the roof sheathing.
1. At the vaulted ceiling area, I need to use 2 Accu-Vent baffles to get the baffles above the top of the insulation. Should the lower edge of the top/upper baffle be installed above the top edge of the bottom/lower baffle, or reverse, or does it matter? In another thread, one person suggested “shingling” the baffles in case there is ever a roof leak so that the water will run down the side.
2. I am assuming that the small penetrations/tears for where staples fasten to the sheathing are not an issue, since there will be air flow at the underside of the sheathing. Correct?
3. If I provide caulk to try to get air-tight drywall, it seems like going on the bottom of two top plates would create a better air seal, since the Accu-Vent baffle has the lip on the bottom.
4. What is the best way to get the joint between the two baffles air-tight…caulk, spray foam, something else?
5. Any other tips, advice, or lessons learned?

Thanks to all,
David