I now have all 6 solar cells operating and finally have an idea what they will actually do. This is between Toronto and Quebec City so medium high latitudes I guess, sunny with significant cloud or rain 1 out of 3 days or so. There are 6 panels rated at 70 watts each in a 24V system. They mounted on the dodger and deck and cannot be aimed.

I have gotten a maximum of about 9.5 amps charge (at about 26 V) through the Blue Sky MPPT controller. 6-7 amps frequently, though it doesn't take much of a cloud or overcast to cut that to 3 amps. As a sort of test, I didn't plug in when we arrived in Quebec on Saturday with the batteries fully charged. With pretty much no attention paid to energy conservation, the battery state of charge was still 75% when I left the boat the following Friday. This is running house lights (not too much, since it is light from 5 - 9:30 and we were usually out on the town later than that), refrigerator, freezer, inverter on all the time charging computers & cell phones and frequently running a small 110 volt fan all night, occasion use of the forward air conditioning (which is also 24V). I never did plug the boat in, I'm sure it will be charged up by the time I get back next week. The only concession I made was to move the booms off center to the south, to minimize the shadow on the cells.

I had learned before we left Toronto that I could run normal lights, charge stuff, and keep the refrigerator fired up with only the smallest attention to energy conservation, and do so indefinitely on the 5 cells that were functioning then. So all in all, I'd say that this sort of install is definitely worth considering.