We do go about installing the roof scoop a bit different here. I never apply fiberglass mat/resin over anything on the exterior of the car. The roof scoop is normally solid all the way to the front of the roof and we leave it that way other than just cutting the opening for the scoop. There is normally a lip on the leading edge of the scoop that extends into the windshield opening and we cut that lip off and just flush the edge of the scoop with the edge of the roof. We cut the sides of the scoop panel down so that there is about a 1" strip on each side of the scoop that contacts the roof, and we take that 1" strip and feather it down to a knife edge. Then we get the scoop positioned on the roof exactly where we want it, drill thru the edges into the roof and cleco the roof scoop right to the roof....placing the clecos wherever needed to hold the scoop tight to the roof. Then trace around the scoop, remove it and rough up the bottom of the scoop and the top of the roof where the scoop makes contact with the roof with 36 grit. We also block the whole roof with 180 grit. Clean everything up and bond the roof scoop on with 3M 8115.....paddle the 8115 into any and all voids along the edges so that it is one solid piece when cured. Once it's cured, remove the clecos, rough up all of the cured/exposed 8115 with 80 grit and apply a strip of short strand fiberfill body filler where the scoop transitions to the roof...where the filler would be the thickest (and also force that down into the cleco holes). Block that down and from there, we pretty much skim coat the entire roof from the door openings up to the roof scoop (also covering the fiberfill we just applied) with lightweight body filler and block the whole thing down.