You might have noticed that objects end up with filenames of the form obj_23.gmt, except for cones with are all called cone#.gmt. If you've ever looked at XPacker you'll see that a moveable object has a drop down menu where you can select whether it's a cone or a sign (signs fall down whereas cones stay upright), so it's safe to assume you can end up with cone#.gmt or sign#.gmt. This is where my experiment began. I imported an object into XPacker, and selected Moveable. Rather than selecting Cone or Sign from the menu, I typed in Building, saved the object and zipped the XPack to BTB. I put the object on my track and exported to rfactor. The object was called building53.gmt (my obj_#.gmt files went up to obj_52). Collisions might be a little difficult to sort out if the object is actually a building. Perhaps a complex object would be the way to go.