There's also a scaling/shrinkage issue with the X axis and Y axis when translating the STL files, where the rendered parts are slightly under scale on those measurements if not adjusted ahead of time (either on the STL or on the ProJet). It's supposed to be constant, 0.55% on the X axis and 0.25% on the Y axis (there is no variation on the Z axis), but it varies from machine to machine. I've been running up against that with the casting masters I'm trying to create that contain hybrid parts. The etched parts are accurate but the RP parts fluctuate slightly, even with the scale compensations modified and calibrated for the specific ProJet machine factored in, and with very little baking to remove the wax. With the Shapeways contractor constantly changing the orientation of the parts, there is no way to get parts exactly right.