I don't use the antenna holes in the SG facia and wanted to fill them in as part of my recent paint project. And I've never liked the bolt head visible below the license plate and wanted it covered for a smooth rear fender.
Here are some pics and a description of what I did. Since I'm no body guy and have no professional experience, don't take anything I say as "gospel," though. Here's a pic of the final product:
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And this is the "before" pic:
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For the SG facia, I used 320 3M Imperial paper to sand down to the black plastic for about an inch around the holes front and rear and feathered this outwards to paint. Using some scrap Evergreen styrene sheet material left over from a model railroad project, I cut four pieces to create two laminated pieces (the sheet material is too thin to use without laminating and used super glue between pieces) and super glued them to the back side of the facia.
Using some Bondo Glass short strand filler, I roughly filled in the cavity of each hole, but being careful not to create areas that would require filing/heavy sanding on the facia itself. I used 60 grit paper to take down the Bondo Glass.
I then filled in the areas with a series of applications of 3M Spot Puddy & Glaze and sanding with 320 and 600 finish. I would prime the work to get a better idea of how smooth the finish was. The right side hole took only 4 or so applications/sanding to complete. For whatever reason, the left side was more problematic and probably took double the effort before it was smooth.
The painter primed the piece and shot it with the rest of my parts.
The bolt head was a similar process, but being that the fender is metal, the work was a bit different. Using a Dremel tool with wire wheels, I removed all paint on the bolt head, the recess, and the area around the recess for about 1" and feather the bare metal outwards to show primer and paint:
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Using the Bondo Glass product, I covered the area:
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Using a file and 60 grit paper, the area was worked then covered with the 3M Spot Puddy & Glaze:
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The "apply glaze then sand process" was done several times along with applications of self-etching primer until the fender was ready for paint:
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The work, which wasn't all that much, was well worth it to me to be rid of the facia antenna holes and the bolt head. It may not be the kind of mod that many people will notice and there is virtually zero "wow" factor in the result. But it sure cleans things up IMO.