@BokaSyn77: Thanks. I find I'm learning a bit more with each map I make, so I'm enjoying it too. When I'm all done I can post a .pdf, sure. That's how I use these maps myself. The problem is, I print them at work on the snazzy color laser printer and I need to do them all at once, preferably under cover of darkness.
@Avengeil: With so many different elevations in these maps, I couldn't think of a way to use color to meaningfully differentiate the heights without turning it into, as you say, a circus. The warehouse map way back in post #3 had 5 different levels, only 2 of which needed coloring, so it worked there. I didn't use a goofy font for the labels either - I just wanted something to convey the height without detracting from the look of the map as a whole.

Anyways, the results were too big to post (11+ MB). My bad.
I've posted them for viewing at my DeviantArt gallery:

M6 - The Grand Cathedral (100 px, Grid)
M6 - The Grand Cathedral (100 px, No Grid)