Why would you need lexan with a metal panel? Have you ever played a real Centipede machine? They don't have lexan.
The only reason any game has plexi/lexan on it is to cover up old holes in the control panel from previous conversions. There is just no real reason to add it to a panel that doesn't have holes in it (unless you really think making your own overlay with an inkjet printer looks good).
Okay, first answer: Yep, I have played on a real Centipede machine - hey, this baby has been most of my inspiration to build such a cab!
I have no other choice then printing my own overlay anyway - to support Missile Command I want to make a layout most similar with Centipede but with three action-buttons. My DonkeyKong-Panel is also a modified print from the original one - check it out on my homepage, I think it could look worse!
By the way, my cab is .5" more in width then the original Centipede, due to the diameter of my monitor-rotating mount. So an reproduction wouldn't fit either there.
These printings don't cost me any cent - so this is very helpful. I can print huge pieces up to 60" width, but unfortunately I can't print on vynil here as we don't have pigment-ink. That's why I've to cover the artwork with lexan. I laminated the last one, but you wouldn't like the look and feel of them under your hands. With lexan over it, it get's a clean look.
For the metal-coldness -an original machine would warm up quickly I guess - not sure if my cab ever gets so hot inside.

I thought about just adding black vynil to the trackballpanel, but this would look dull.
@Birdtales
Great, thanx a lot, man!

I'm pretty sure I've seen such a bit with bearrings in the package that came with the router!