Help, change ratio of parallel lines in trapezoid?

I am trying to make a triangle (think the old food pyramid) where I will produce several versions of the visualization with horizontal slices completely missing. Each of the 7 levels in the triangle should be a constant vertical width. I thought I would use trapezoid shapes stacked on top of each other capped with a triangle shape. This would make arbitrary sections easily removed. Since the parallel lines of the trapezoid shape appear to maintain their ratio, if i change the height of the trapazoid, to maintain the constant vertical height requirement, the angles of the sides change, thus making a terrible stacked triangle.

Am I approaching this the wrong way? Should I just make what I want with lots of lines? If I could change the ratio of the parallel lines in the trapezoid shape, I think I could get what I want, is that possible? Any suggestions of how to achieve my goal would be appreciated. Thank You,