Another thought: you're in the frigid north, where heating is a necessity in winter. Even though you already have a Webasto diesel heating system, you may want to consider the following.
Many/most marine A/C units with heat use a heat exchanger system, drawing heat from the water. These work OK as long as the water isn't too cold, but require moving water (pumps) continuously.
After considerable investigation, a few years ago I chose to install the same units used by the USCG and Canadian Coast Guard...those provided by Flagship Marine:
Marine Air Conditioning Systems - water, air and keel cooled.
These have the option of using a large electric heating coil instead of a heat exchanger. They work beautifully. The coils draw 2,000 watts, and just one of these keeps my 42-footer warm on most winter days. I have two units (16,500 and 12,000 BTU).
A friend who lives aboard a similar sized boat also chose the Flagship units, and has been very happy.
And, their pricing is very good and the packages include just about everything necessary for an install....all quality stuff, not cheapo junk.
I also have an Espar D5L system which by itself can keep the boat toasty in any weather. However, the electric heating is clean, safe, very convenient. On very cold nights (like <10F) I sometimes set the Espar thermometer about 5-10 degrees below the Flagship heater thermometer, so in case of power failure or other reason the Espar will kick in if necessary.
Just a thought....