Our friend Klaus Hafner (make sure and check out his aluminum river boat build) pointed out a book that might be of interest:

Bruce, found and already read this book.
The Warm Dry Boat, by Roger McAfee
Some very good informations to deal with venting and heating boats,
discussing different techniques and efforts.
Maybe you are interested to offer, was not possible to get it from Amazon,
just a used one for more 100$
I paid incl shipping to Frankfurt ca. 50$
Br, klaus

This is the contact
Navigator Stove Works LLC [marinest@marinestove.com]
Andrew Moore
Navigator Stove Works LLC
509 Double Hill Road
Eastsound, Washington.
98245 USA
Ph. 360 376 5161

The Navigator Stove Works, Inc. web site referenced looks quite interesting and detailed. Keeping a boat warm and dry always seems to be a challenge. New/good ideas for maintaining your living spaces is something to keep abreast of.