Not sure if it's memory management or video driver. I can overlay 2, 3 or 4 complete sheetmetal underbody assemblies of a car in CATIA and NX, shade and rotate and work (aka design tooling) with no hick-up's or issues. Inventor can only get about 3 or 4 parts before I get lag. I shouldn't have to create separate shrinkwraps either (most of the time they not create anything useable anyway). This should all be done in the back ground. Load light weight and automatically switch to full design is file is made active.