do you mean something like this? OR doesn't do slots, and it really doesn't like the fact that there is no nose cone . not to mention that it is a little clunky to import your 'custom components'(though I suppose one could open the component and build forward...). you basically build the upper section, go to the file menu/open, open the component(in this case 'fin can'), select the body tube, edit/copy, then switch back to the window where you are working on the rest of the rocket and paste the fin can onto it. one can do this sort of thing with other items(like fins).
did this answer the question?
Rex