Walther's Standard Pullman lighting kits

[twhite]

I'm in the process of putting the Walther's lighting kits in my Pullman Standard train, and I've noticed that the aluminum heat sink that comes with the kit gets REALLY hot when you turn on the power. I've only done three cars so far (six to go) and I wonder if anyone's used these kits with their Walther's Pullmans, and if so, has the heat-sink caused any damage to the plastic ends of the cars? I really don't want my "Prospector" to start melting halfway through its run.
Any comments? Or am I just being paranoid?
Tom [:p]