Gray,

Are you using the flap channel as the master and the elevator channel as the slave? If so, I would suspect that the elevator can not be made to move because the flap channel is at its "zero" position at takeoff setting and 0 times any percentage is still 0. If you want a fixed amount of up elevator with takeoff flap, use "offset' as the master and "elevator" as the slave. Enable the mix with switch "C" in the center and dial the percentage you want for the required elevator movement. You should always be able to get a surface to move a fixed amount at a certain switch position with a mix with "offset" as master...

Bob