Re: modified v vs jon boat
You're right that traditionally, a jon boat (not John) has a square bow and flat bottom. However, nowadays, a lot of people call a small (12-14) open hull boat a jon boat, even with a deep V or modified V. But there are jon boats over 20'
In theory, the flat bottom can run in shallower water and the V "slaces through the waves." In practice, especially at 14', they draw about the same and a 14' boat isn't doing a lot of slicing. But look at the deadrise at the stern, and you will see how much more the various V hulls require.
As for skinny water, it's not so much what you can run in, it's what you can pole in, or walk the boat across. An extra 2" does not determine whether you run full speed on a plane over 6" of water.
the real advantage of the jon over the V is that the jon is way more stable, which is important in a small boat for fishing or that you will be moving around in to pole, etc.
Look at the Chincoteague Scow--that is a superior design, combining the best of all worlds: seaworthy, flat, light, stable, shallow draft.