I wonder if you made a frame, on the sides make the "stepping" of the siding.... then ran lines of an elastic from the bottom of the "step" on one side to the other, then.... run a big piece of nylon or some other stretchy material over the whole rig attaching it to the pieces of elastic and the sides, it would create a surface that would stretch back to normal and you could even back light it to give it more effect.... if that made any sense at all.
|\ < the frame would look like this on both sides, you could stretch
|\ the elastic from the underside of the ridges on one side to the
|\ other. then stretch the nylon or whatever over the rigging
|\ stapling it as many times and places as possible on the way
|\ down both sides. you can then attach the elastic to the nylon
|\ a fabric glue or if you are so bold sew it.
sorry i couldn't draw with text better, hope that gives you some directions to go or ideas to hatch out. ~Flesh
"The last man on earth sits alone in his home, then there is a knock on the door...." John Carpenter