It's perfectly understandable that many here believe the fins are faster when adjusted to the tight position. After all, that's what the Hobie instructions say. Moreover, Hobie initially set up the Turbos this way for the first Pro Angler boats.
The concept was based on some of the faster fish, so if you're pedaling along at about 20 MPH or so, it would probably work fine. Unfortunately it just doesn't happen that way in the kayak speed realm that we operate in.
Now in their 3d generation, the current Turbos are more forgiving of an overtightened leach than the original version, but the difference is still very noticeable, especially over time and distance.
As Iterrero indicates, the fins rotate much like a prop blades, needing more twist as the cross section gets further away from the hub (sprocket shaft). When set too tight, the fins are over-pitched and feel like you're batting boards back and forth -- indeed, a large part of your thrust is going straight out the side and providing lots of extra exercise for the pedaler.
IMO, the ideal fin setting should be as loose as possible, with the clew anchored in the outhaul pocket by about 1/8 inch. This maximizes the twist and allows the fin to wind up the mast about 1/4 inch (assumes your mast is not bent).
This setting gives you greater speed/range over time with much less fatigue while maximizing your acceleration as well. It will also give the fastest sprint speeds. Running at a medium to fast cruise for 1/2 hour or more the difference is like night and day.
I used to think the rear fin should be set slightly tighter than the front fin. Technically this is true since the rear fin plays off the front fin. But in reality, it's insignificant and less important than maximizing balance betwen the fins (overtightening one fin tends to wiggle the boat slightly).
There was a fad in Austrailia where it was thought running an ST in the front and a Turbo in the back was the most efficient. While easier to push, it's not as fast as two matched Turbos.
Finally, the loose clew concept is valid for ST fins as well, and even more important for optimal performance.
Personally, I like to go fast. During races, I modify the Drive to open up the pitch even more. But that's another matter.
