My friend built a stick built house with cathedral ceilings and used tounge and groove 1x6 on top of the exposed rafters, on top of that roof he built another roof and insulated above the 1x6 between the other roof rafters. Then he decked that roof and shingled it but it allowed him to put more insulation in there by having two roofs. From inside you see the one roof but from the outside you only see the upper roof. We built the loft and installed the log siding that was all cut from his land. The loft was supported by 4x10 rough sawn larch if I remember correctly, 24' long. They were not any fun to install but it looked great once done. Your home is going to look great once your done and I look forward to following this thread as you keep updating it.