A month or so ago there was a thread about how to correctly restore a targa top. There were many different suggestions. I emailed Porsche classic (the in house resto division) to get the "official answer. Here it is:
Dear Mr. Ziegler,
thank you for your request.
We would like to inform you that you may use an ordinary paint in order to restore your Targa top.
If you need a technical documation please have a look in relevant literature which you can purchase
at your local Porsche Center.
Yours faithfully
Jochen Bader
Manager Workshop Classic
Dr. Ing. h.c. F. Porsche Aktiengesellschaft
Porscheplatz 1
D-70435 Stuttgart
Telefon: +49 (0) 711-911-25090
Telefax: +49 (0) 711-911-27592
E-Mail: jochen.bader@porsche.de