Hi chipp, I downloaded all your car materials and think they're great. One link however is dead I think. "http://www.gadgetplugins.com/chippstuff/CW_CarPaintGlossy.mat". Could you check it out? Thanks.

Also, in your render of the red rocket ship, did you use the hdri map as your reflection map as well or is the light box the only reflection?  What hdri map did you use for that? I'm trying to look for a similar map (i really dont like the sky maps for car materials).