Compose will let you take the custom geometry from a CR2 or other Poser library files and let you save it as an .obj, but it doesn't effect the CR2 itself. I know that with CR2Editor you can delte out the embedded 'geomCustom' sections, but I don't know if CR2Editor will then write the storageOffeset and geomHandlerGeom lines.

Kevin has a great CR2 tutorial if you want to learn more about the format. I don't have the link on me...and I'm not even sure if his site is up right now...but hopefully someone here knows where you can find it. You can also learn a great deal about CR2's just by looking at them in a text editor. You can easily do what you are trying to do by hand...CR2's are easy to edit, they're just hard to explain. Whatever edits you make, just make sure you are doing it to a copy and not the original.