I wouldn't make them a prop or a conforming item, I'd make them a group in the main CR2, with an external CR2 call if you must (be better in the main OBJ file, though). Big advantage to this would be the operators would we listed with that part right in the main item, plus I think in the long run it would be easier to set up. I did a sailboat once with an hinged front hatch, plus a companion way cover that slides front to back, plus two doors under this hatch that slide to the side, didn't take very long to set up, and once you did one you could clone that group in the CR2 and just move the centers (simple math) for the next one. I also removed all the channels I didn't want used and forced limits so nothing opened or shut too far. If you are doing an _exact_ fit for the door you are going to have to set every one up individually anyway.