Thanks for the explanations. My problem is that the design I have started in May has 8 levels (=map files). But this is because I tend to divide areas in more levels than neccessary (just to keep the overview), and because I sometimes use a copy of a level for a later visit (that means, when the party returns to an area, they return to the copied level with slightly changed walls, other events and different background music, all to emulate that things in the area have changed a little). For the player, it would look like four areas only.
If this is okay, I could take part with the design I am just working on. If the 4-map-files rule is strict, I could instead join with "Snow Tigress", which I wanted to contribute to the winter contest but could not finish in time. But now, this design is already 98% completed.