On my 2003 Brave, I had roof top heat pumps with the output to ducts that ran the length of the MH. Any chance of getting to one of the ducts and going the length of the motorhome to the back? I believe that I read about someone doing this in another thread.
Also, Is it possible that the coax is already there? Winnebago may have installed the coax for the rear TV even if it wasn't ordered as part of the factory order. You might want to check with Owner Relations to see if the coax is already there and where it m\is located.
W8RLM - Bob
2006 Winnebago Journey, Model 39K, 2013 Dodge Dart