My car originally had a luggage rack that the PO removed. I don't like the look of the luggage rack as much, so I was OK with that. However he covered the holes with black electrical tape. Eventually I'm going to get the car repainted, and will weld the holes over at that point. However I needed a cosmetic solution that was a little more sophisticated than electrical tape. Here's what I came up with:
I put a dab of silicone on each one to keep the water out and plugged them in. The 3/8 inch was a fairly tight fit, but I eventually persuaded them to go in. Here's the trunk:
It's not as good as a smooth painted trunk, but it is a way to fill the holes that looks reasonably finished.
A.J.
1974 Fiat 124 Spider
2006 Corvette
1981 Spider 2000 (sold 2013 - never should have sold that car)