Doug, I would recommend just have another good look through the wood board covered openings of the aft berth floor. I did not have conduits either (maybe the boat dealership installed the marine head on my boat). I routed through the floor without any problems a pipe for my cockpit shower and several conduits for all kinds of cable like solar power or a second battery. You can see the battery cable in the first and second picture in my previous post. You should have any no trouble going going from the bathroom all the way into the area behind the vertical aft berth wall.
Hart
Hart