In my little RW 2306 there are actually ducts cut into ceiling for vents in the bathroom that were sealed up and not used. Was told that they use certain roof systems for many camper models. Maybe there is a chance you have ducts already in the ceiling. Pull off the last vent covers before the bathroom and look up in it.
There are 10 types of people in the world.
Those that know binary, and those that don't.
2013:31 / 2014:51 / 2015:58 / 2016:37 / 2017:46