Thanks for a good solid data point.I installed an Espar Airtronic D(iesel) 4 back in 2004.
Based on your experience with a boat of about the same volume as mine (32' x 10'), do you think a single duct exiting at the back of the cabin right at floor level would give me reasonable results? I know the head will be colder but I can live with that. It has a louvered door so I could put in a 12 V exhaust fan (a good thing to have anyway) and a removable cap for the dorade vent that enters it and suck warm air into it from the cabin when needed.
"Reasonable results" means there won't be anyone on board who is expecting home style comfort and heat and who will squeal if they encounter a slightly cool spot.