I prefer last years black strip at the front alas still a very nice skin, ive been doing mock sebring races with the ai and its gone rather well so far.
Great.
About (missing) previews...
you have to rename your skins folder from "Porsche Team North America 912" to "Porsche_Team_North_America_912" - there must not be any empty spaces in skin folder name. It's simple as that. :)