Hi... Yes, it is very common for the turns to be different. As part of the tuning process on the Mad Dogs we were always fiddling with the port size, this allowed us external control. In general, for Alphas where the port is less than 3 turns open, one full turn is about 2dB. On some Alphas the port is over 3 turns open and then the result of a full turn may only be 1dB. In short, the more the vent is open the less the relative increase for each additional turn.
This is part of why this is an unsupported feature. We can guarantee it lets us match channels during tuning, but there is enough variation in the Fostex drivers that we can't guarantee how much bass can be added, though there is usually an audible increase that can be obtained.
Thanks for the quick reply. This is understandable (as I though it is, finding the correct balance without instruments is almost crazy)!
Can someone ordering from you directly (the site) order his pair to be +2db lets say more from the 'factory' tuning that you do? So the default will be +2db matched in both sides by our team?