I'd look into a SR 17 footer, I paddle 16 tandem solo, but for a tandem canoe I think the 17 might be a better ticket. Depending on your physical size/weight and gear you take, the SR 16 tandem might fit you also. I've taken the 16 with another paddler, 2 big portage packs, plus food pack and a couple of day packs, had plenty of room but I think you could solo the 17 if you ballast it out properly, and with two people, the extra foot would give you a better paddling speed.
I have to think the off balance problem was related to the yoke position, perhaps it was mounted too far off center?