As much as I like OpenSCAD for its scriptability, the OP is really pushing the limits of what you can do with it. I'm hoping FreeCAD takes off eventually in thi

As much as I like OpenSCAD for its scriptability, the OP is really pushing the limits of what you can do with it. I'm hoping FreeCAD takes off eventually in this space (hobbyist parts design). Of possible interest to those reading this, I worked on a project in college that did a similar thing with AutoCAD for full-size water treatment plants. A web interface[1] accepts input which is sent to design scripts, where equations of fluid dynamics and other physical constraints are used to scale components appropriately for the size requested. From there, the AutoCAD command prompt is accessed to generate a 3D model and various construction-oriented section views. [1] http://aguaclara.cornell.edu/implementation/design/ http://aguaclara.cornell.edu/implementation/design/