Use a rectangular needle file to make the pushrod channel by
expanding the guide hole. The channel must be elongated vertically
to provide space for the pushrod travel up+down during the aileron
deflections.
The needle file inside the servo pocket. You can reverse the direction
and expand the channel from the pocket side also.
Trial fit the control horn in the slot. Do not glue at this time.
Sharpen slightly the end of one pushrod wire. Then make a sharp
bend about 3mm from the end.