I think your, going to have to mask it off. Sand it down smooth. Repaint it on the roof. Here’s a unpainted new part. You might have to go to a convertible top shop, have them remove the spoiler, from the canvas top.
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Fiat 500C Spoiler. Rear. [no description available], [soft top - black], [soft top - - 1WC13KX6AA | Libertyville ILSpoiler. Rear. [no description available], [soft top - black], [soft top - black]. Color: [no description available] exterior: [po0]. Fiat 500C. Genuine Fiat Part - 1WC13KX6AA (1WC131X6AA, 1WC132X6AA). Ships from Libertyville ILwww.mymoparpart.com
Thanks. I didn't even know what the part is called. I will try the sand and paint suggestion, one of these days ....
Mine did the same thing (2012 black top). I have not seen any red or black roofed 2012s or 2013s that have not had that happen. I did have to have the roof replaced a few years ago. So far so good with the new one. I learned in that process that the entire roof unit is one piece...over $5000 part!