Pelican's a pretty boat and it looks pretty similar (if bigger) to what I had in mind. I was thinking a modified triloboat (triloboats.com
) insulated with 2" blue construction foam board. Lee boards for lateral resistance and either a junk cat-schooner or sprit yawl, though a gaff ketch is not out of the question; I just don't know if I'm up to building a rig as complex as a gaff of this size, yet. I'm leaning heavily toward the sprit yawl because it's so simple with very few strings to bother with and is relatively easy to scandalize in all weather.
The RMH would essentially be placed where a centerboard case would otherwise go. In a boat this size (20x8 -ish), the bench wouldn't be too terribly much wider than a CB case, but would be lower, so I could use it as shelving below a countertop/table arrangement ... or whatever. The cabin furnishings would be designed around the heater and not vice-versa. Center cockpit with heater below. Head off to one side, aft stateroom with big open plan saloon and galley for'ard. Genny and batteries below saloon seating and tanks 'neath the double berth in the stateroom.
It's a full-displacement hull form, so not too much worry about overloading it, so long as I get my bow and stern lines/curves high enough so the transoms don't push/drag water when in motion. I may or may not include a cutwater at the bow, but a transom is so much easier and faster to build.
As to the idea of a multi-channel flue system in the bench with a bell at the far end, the idea was to use those large multiple pathways to reduce any goofy draft issues from being constantly in motion (even when moored.) That's also why I had thought about nine-inch total diameter in the flues with a six inch burn area - lots of choices for the gasses to flow around. Now I think on it, though, it probably would lead to backdrafting smoke because the refreshing hot gases aren't helping as much to push through the system. I'll have to have another think on that.