Chris, that is great information! As noted, I have substantially less experience with ST fins than the ST Turbos. Most of my ST data is comparing it with Standard fins at different speeds, and differential comparisons with degrees of freedom allowed at the clew (example below; note the added link) for which I was using the clew adjustment specifically to alter foot travel rather than fin twist. There is a lot left untried!
Since I use Turbos almost exclusively, my specific
clew adjustment trials are with Turbos. Additionally, I have no performance experience at all with the newer more durable fin composition for STs. With Turbos this makes a difference, and would guess it also has an effect on the STs.
In looking over my notes, I can also confirm that a stiffer fin with STs may add more speed (but also a greater pedaling effort). This is exactly the opposite from the Turbos for the possible reasons I mentioned above. As with prop blade length and pitch, STs exhibit a different performance pattern.
I also reviewed my notes regarding Tom's comment. Specifically (again, using Turbos), as I tightened the front clew, speed change was negligible but pedal effort increased markedly. Resetting, then tightening the rear clew, speed change was also negligible and pedal effort increased to a lesser degree, but at the extreme, the boat started yawing with cadence (which was held constant at 40 CPM). My specific conclusion -- for cruising, given the same cadence, tightening Turbo clews does not impact speed significantly, but does increase effort, therefore fatigue. Over an extended time, looser clews will facilitate a greater range specifically due to the fatigue factor. At sprint speed, tighter clews actually slow performance by inducing a lower maximum cadence.
I have had slightly better one hour times using an older, stiffer Turbo on the rear, but this year I'll try Tom's idea with the stiffer fin in front and see what happens. Fin stiffness is simulated by clew adjustment, but there is some difference due to allowable degrees of freedom at the foot (more allowable foot movement gives more speed).
I think your comparison is excellent and it's great to see someone else taking the time to try some of this stuff. I hope more folks will experiment and share their results.
PS: As you may surmise, Drive performance is my favorite topic, but probably boring to most here on the AI forum. Sorry if I get carried away!