On the early Stealth rudders the horizontal fin is about 12cm long each side of the rudder with a root width of about 5cm and they are symmetrical.
The newer ones are much smaller with a fin length of about 9cm and a root of 5cm.
I set mine up by adjusting the stock so that the fin is neutral with the boat very, very slightly bow down. This way I theorise that the T foil doesn't interfere until it absolutely needs to - maybe that's why there's that 'famous' picture of me with a bow wave at the mast base?????