I had the same problem my first time out in my i14t but the fix was not so simple as using the cleat. There is interference between the stern of the boat and the sailing rudder such that it won't go past a certain point. I'm committed to only turning left or only turning right depending on which side of the stern the rudder is on when I cleat it down.
I went back to Next Adventure Paddle Sports and it appears that there is the same interference when the sailing rudder is mounted on another mirage drive inflatable they had on display. I think it was an i14t but it could have been the i12 we were looking at.
Second time out I used the regular rudder. No interference but difficult steering in more rate winds to say the least.
Will upload photos to this gallery shortly: http://craigstrong.smugmug.com/Other/Ho ... 019_HHsFD5