Thanks for your inputs guys. I saw in a recent issue of RC Car Action where they demonstrated the translucent polycarbonate paints. So I'm thinking of trying PS-38 Translucent Blue backed by PS-12 Silver to achieve the dark blue metallic effekt.
Back in the 80s before polycarbonate paint was available I succesfully used normal paint on the inside of polycarbonate/lexan bodies. If you sanded them well before applying the paint, it actually held up fine.
The Clio is destined to be a shelf queen, so I might go with Swarm's suggstion of using regular TS-53 paint.
We need a procrastination emoticon