something you guys might think about is... going to your local trim shop and looking at their marine vinyl ( weather resistant,) and match it up to your paint. have them make you piping like they use for seat welting >>> you can get it in many different gauges and it works great. if the car won't see much weather ... you can even use auto vinyl.
I know it works, I make it all the time for customers building rods and vw's !