Ah Charlie,...that would be a "Val" - ance.
I agree. Anything you could do in the future to hide the light bulb and just allow the visitor, and you, to see the effect of the light would be a plus. Easier on the eyes and helps focus everyone on the layout. Also, your eyes will perceive the depth of color better.
Concerning the moisture issue raised by Beig. Just to be safe, leave the bottom of the cavity and the top of the cavity, behind the masonite, open so air can circulate behind it. This should alleviate any problems. There, got to use my architect stuff with my train stuff! My momma would be so proud!
Really enjoying your photo essay.
Keep it up!
Ted