Porsche 959 question

OK, I am very close to completing Tamiya's Porsche 959. Does anyone know how the underpan should be finished? It is an aerodynamic panel, and the directions say to paint it body color. Is this correct? If so, should it be flat (not gloss-coated); should it have undercoating or anything? Thanks.

I just completed mine and posted it in the gallery this afternoon. I couldn't find anything as well on the internet so I decided to leave it gray.