This might be the answer to all those who place windows and doors in SketchUp. From a great script write over on the SketchUcation Forums:
http://forums.sketchucation.com/viewtopic.php?f=323&t=30846This script adds a new tool for glued/cutting component-instances.
It allows them to punch linked 3D holes through the faces of double-skinned walls/roofs etc.
I plan on testing the plugin next week.