hello for plywood two coats will be needed. regarding the seams. here is the procedure for this. You would apply a linear line along the the seam with our SeamTight and embed the fabric and let dry. Then the next day coat over the fabric with the SeamTight and let dry. Then you can apply the RvRoofMagic over the entire roof. That way you are totally encapsulating the fabric and you won't have to worry about that seam again. then your first coat of rvroofmagic let dry then apply the second coat
Thank you