I got it to work.. After you SketchUp your design, go to File, Export, 3D Model.. Save it as a .3DS file. Open Falcon, click the car, import your design.
However, according to Falcon, an S10 like mine (with ridiculous body kit, courtesy of the Warehouse model) lowered with simple cap and angled nose can achieve a 0.37.. I tried it without the nose first, and it said 0.50 CD. Intriguing to play with though, thanks for the find.