Athena 38: Diesel Hot Air Heater Location on Athena

[Rapanui]

I want to fit a diesel hot air heater on the Athena for the chilly evenings and mornings early Spring and Autumn and would be grateful to find out what people have done with their Athena.
My plan is to have a unit that heats only the port hull and the saloon which is what we do now with an electric fan heater when on shore supply.
The obvious place to fit it would be on the fwd side of the engine bulkhead in the underbunk stowage in the aft cabin. Diesel supply is adjacent at the primary Racor filter. Hot air to the aft cabin is easy, A run fwd under the floor to get heat to the fwd cabin and WC compt seems doable and there would seem to be a way to get hot air to the top of the steps via the wardrobe/shelves unit to heat the saloon along with warm air rising up from the hull. My concern is where to run the exhaust/inlet pipes to the outside. Direct to the hull either on the inner or outer face is easy, but they would be close to the waterline which seems wrong to me on many counts.
The only other obvious to me option is to fit the heater in the aft locker on the aft face. Diesel and exhaust/inlet will be easy but getting warm air into saloon and hull looks difficult with very long runs.
I am sure others have done this and would welcome their experience.