Don't put the link at 90 degrees to each other on the servo. Put it at say the 10 oclock and 2 oclock positions. You can use the star wheel and put it off center. That will give you more one way than the other. You just need to make sure to use the right side to get more up than down. You can also move the horn on the aileron itself to acheive it, but it is better to do it on the servo wheel.