I've thought of this mod, but the downsides I see are perhaps excessive noise, and too much light entering the bedroom. I recently added roof a/c to the living room area, and cut a new hole. pm me if you want specifics on cutting thru the roof. Winnebago runs the two a/c ducts front to back off-center, you can easily identify those. Steel cross-stringers side-to-side are present, and Winne can email you the engineering diagrams. The easiest way to locate them is a stud-finder from above. My coach had a wire chase curbside from the curbside a/c duct, again identified with the stud-finder. There will be wiring(coming from somewhere) to feed the ceiling fan/light. These could be reused to feed the Fantastic. There's no reason the Fantastic would need to be centered, or need to eliminate the ceiling fan, as long as you avoid the previously-mentioned structural items.
I've been experimenting with using two 120mm computer fans hanging from the top of the bedroom door frame, blowing cooler air from the hallway area into the bedroom. I attached them to a small square of corrugated cardboard and blue tape to test my idea, and they have been hanging that way for about a year now! The fans are only about $10 each, unobtrusive, and quiet. So far, so good!!
Kent & Sue & Pecos
2010 Allegro Bus 43QRP
Formerly 2004 Itasca Horizon 40AD