So here is my model. remodeld the pigeon to be long. I've been experimenting with the JBeam. Since I have extended the frame, body, axel, and exhaust pipe I'm going to have to change the jbeam. I have messed around with it a lot. I have also used the BNEditor. For example to maybe do it - have the extended frame in blender and than use the jbeam exporter plugin? I've done a lot of research in past few months but maybe not enough. haven't found anything on the wiki that fits what I'm doing.
The blender plugin can only export and not import so you will have to use another tool. I think you should duplicate the structure of the cabin