You can always open the prop file in a text editor, scroll down to the "f" section (the last) and change things by hand. g _____ is a group (the overall name of the prop should be g NAME at the beginning of the "f" section. usemtl ______ are materials. Delete one and the section will be a part of whatever usemtl __ is last above it. Delete all usemtl lines and Poser will assign it one material: "Preview"