I'm not sure about the hydrodynamics or water displacement theories, but I do know that a wider boat will be more stable. I have fished 2 people, standing, in a 1236. However, both people have to be very used to being in boats and had to coordinate movements. When both people are sitting and not fidgeting around, it was fairly pleasant. If you keep the weight as low in the boat as possible, it will be more stable. That's why it is more stable when you sit and also why most people don't recommend decking a boat that is narrower than 36".
I recently sold a jon that was a 1430. There was nothing that I could do that would make me feel comfortable taking it on my lake. It was tippy with just me, sitting, and basic gear. It wasnt far from being a canoe. The 1236 at 2 feet shorter and 6 inches wider, was much more stable loaded or empty. That's just a 6" width difference. Going from a 1436 to a 1448 would be even more stable.
My current boat is an old Arkansas Traveller that is 14' x 57". I have no issues with stability, even on a busy lake. I doubt I will ever have another boat that is less than 40" wide unless I have a private pond or flooded timber.