RE: Which servos center really well?
How do you know it is not the pots in your transmitter sticks that are causing the centering problem? I have tested some servos for people that were having centering problems using a computer to simulate the pulse coming out of the receiver to eliminate the transmitter. Doing this I have found that a lot of centering problems are in the sticks of the transmitter not the servos.
In measuring servo centering error I have found a good part of it is hysteresis. So now the centering specs can be part of a game of how it was measured. If it is always measured as repeatability coming from the same side to center it will look a lot better than if it is coming back from center measured from one side then the other.
I know this doesn't answer your question but it is something to look into with servo centering.
Pete