I'm adding a non-loading bearing interior wall to accommodate a built-in electric fireplace. The new wall will run parallel to and 4" off center from an existing ceiling joist. Rather than adding blocking between joists (not easily accessible through the attic floor), I'd like instead to use a 2X8 as the top plate for the wall (i.e., make up the 4" offset with the wider structural plank.) Has anyone ever done this before? Would appreciate any lessons learned. Thanks.