A site model

I'm having a terrible experience now. I’m making a site model for my assignment and it’s awfully terrible, because the site is a mountain with sheer cliffs. Why is it so terrible? 
When I make a site model, I use styrene paper 5 mm thick. This time I am making a one to two-hundred scale model, so it is scaled down to 5 millimeters for 1 meter. The height of the mountain is 72 meters, so I need to pile up 72 styrene papers in a contour interval. If I simply pile them up it’s not so hard, but the styrene paper is expensive, so I make it by using only two papers. How? 
First, prepare two site plans, and trace on every other contour line with a red felt pen. Shift one line in another plan and use a blue felt pen. Next, put up plans on each styrene paper, and cut the styrene paper along the colored line. Then, pile up the red and blue ones one after the other. Finally, the mountain is complete! 
It seems not so difficult, yeah, it’s easy when it’s a gently sloping mountain, but in case of sheer cliffs, it becomes hard, and that's 72 papers. 
My work stopped at a part of the gentle slope. The future is black!