Jake, you said, "As to why you can make better headway upstream when paddling at 45 degrees to the current, I have no idea."

Isn't water current basically the same thing as air current (wind), except a thicker medium? We are best able to make progress upwind with sails by having approximately a 45-degree angle of attack to the wind current (and most of us don't REALLY understand that one, either.) So why couldn't the same thing be true of a boat hull going through water when being paddled or motored? I would think it would be especially true of a Hobie 16 because of its asymmetrical hulls. If you did not have a sail up and you were paddling a Hobie 16 at a 45-degree angle to the current and depressed the up-current hull enough to get the down-current hull out of the water, wouldn't the boat literally "sail" up-current just as our sails do through the wind current?

Just another of those dumb questions that keep me awake at night. In fact, now I am visualizing an invention of a boat with an underwater profile that will allow it to literally go up a creek without a paddle.