Most efficient - paddling or rowing?

I forgot to mention that my Voyager is difficult to turn. It wants to go in a straight line. I was limiting this discussion to no wind, but on the subject of directional stability, a headwind or tailwind can catch the high sides of the canoe and you have to paddle extra hard on one side to keep on course. If you can set your course directly into the wind, it is easy to hold a steady course.
My opinion is no skeg necessary.
I know of at least 2 Voyagers that have added rudders (for competition).
Rudders and skegs are not factory options.

 

SailorDon, as you don't do sit inside kayaks have considered trying one of the more stable surf skis such as an Epic V6 combined with a small wing paddle? http://www.epickayaks.com/product/product/epic-v6
A wing paddle uses a different stroke to what you are used to, there is a detailed description at
http://www.epickayaks.com/article/article/bartons-forward-stroke
There is an Epic dealer in Houston who may be able to organise a demonstration. http://www.kayakinvestors.net/contact.html
I don't have any relationship with Epic other than my wife having a couple of their paddles, I just chose them as a readily available brand that has good designs.

My averaging 5 mph probably has more to do with my Guideboat being half the weight and a bit more efficient than the Thames Skiff rather than fitness. The design is this one http://www.guillemot-kayaks.com/guillemot/other/adirondack_guide_boat
If you look at the performance tab you can see that the drag is still quite low at 5 mph. In an all out sprint it peaks at around 7 mph. I certainly don't consider myself fast and would be lucky to make midfield in a race. Back when I was a very skinny teenager I could paddle 10 km in an hour in a wildwater racer under 15 ft long which is 6.2 mph.

 

Even 20 years ago when I was "at the top of my game" in competitive sailing, I would have had a real challenge staying upright for 5 miles in an Epic V6.
Now as a secure member of the geriatric set, I would be upside down so fast, it could be timed in fractions of a second.

I demoed a Wenonah Solitude before buying my Wenonah Voyager.
The beams at waterline (good indication of stability) are listed below.

Solitude.......30.5".......Good stability.
Voyager.......27.5".......I had to tweak some things to improve stability.
Epic V6........23.0".......Flip-over City!

Me in an Epic V6 just ain't going to work.

Your link to the paddling stroke method was good training for me. I need to improve my torso rotation which is excellently demonstrated in the video.