Well let me think... I paddled the same river under the same conditions (or as close as possible, I guess) going the same distance. I think the wing forced me to paddle better in order to be efficent. I lost added momentum when I broke down to low angle because I was getting tired.
The biggest improvement was on the upstream. Average speed went from 3.8 to 4.1 (according to my GPS), with some much better bursts. Going downstream with the current, I did not notice vast improvement in watching the GPS, but I believe that was because I started to tire out. I wish I knew the speed of the current.
I think you're right that other factors could have contributed without me thinking about them at the time. Having done the same route the week before, I had better prepared for taking certain bends that gave me some fuss before. I prepared and edged a little more than before, I think too.
I do believe the wing made a significant difference though. Even if was just making my stroke more efficent. Fenn 4 is a fine design and somewhat forgiving. It is a heavier paddle than my Wind Swift.
At one point I was directly behind (but a short ways back) from one of the guys and started matching him stroke for stroke. I steadily gained on him until the turn around point.
I'm just excited about a big improvement in time and getting excited about the race. I still have to be better to be a contender, but I'm on my way (with a wing paddle).