SD300 Mizzing Piece puzzle

This is designed for PVC laminated-object-modeling 3D printers, but it may work in flexible materials on other machines (possibly nylon).

The SD300, SD300 Pro, and Invision LD printers build a \"test part\" that folds up and snaps together into a nice little pyramid. I designed foldable_oct.stl to enable five standard test parts to be stacked to build a larger pyramid. The puzzle is to figure out how to utilize the new piece to make it possible.

NOTE: foldable_tetra.stl is equivalent to