Yeah, my CP is metal. It's 16 guage steel that is carriage bolted to the wood. If I go with lexan on top of the metal, my leaf switch buttons will have a hard time making contact so I'm trying to stay thin. My situation is that I do have a custom printed CP and would like to cover it with something clear that will protect it. I've done many experiments and I'm getting closer to finding an ideal solution. The last one I have yet to try is going to a sign shop and seeing if they have adhesive laminate that has a permanent bond (this was recomended from a fellow byoac member). This is probably the best solution. The next best thing would be to use cheapo clear contact paper and use a coat of spray glue to make it stick better. If I use a light enough coat, you won't be able to see the glue through the clear contact paper.
I'm not really anti plexi/lexan - it's just a personal preference and also a necessity in this case.