Here's an approximation of the bellows / "shock mount" that goes on the bumper of the proton pack from Ghostbusters. I based the shape generally on Stefan's plans, but modified to have 11 convolutions instead of 12 (as is visible in some photos of screen used packs) and a slightly longer length. It's 1.75 in long by 1.6 in OD with a 0.25 in ID mounting hole. I have no way of knowing how accurate these measurements are, but it's what looked good to my eye :) The example in the photo was printed on an Afinia H479, underwent acetone vapor smoothing (http://solidoodletips.wordpress.com/2012/11/10/presto-part-finisher/), and was painted with Krylon matte aluminum.To minimize support material, print in the horizontal orientation as shown in the preview image.