The key with the helicopter blades is the weight has to remain the same, so they spin down slowly and make that cool woosh, woosh sound as they slow. Going to lighter bladed without the metal and nuts and bolts will make it spin really fast and then stop just as fast without the slow woosh sound. The reason I mention this is that I had considered moving the factory blades to the underneath the playfield and putting more realistic looking blades up top. If only the shaft that the blades are mounted on would extend further down below the playfield this would have been possible. In hind sight this would have been the way to design it from the beginning so the extra spinning weight was below the playfield and not visible.