Spektrum says for the carbon cub s2 -
"The DXS does not support Flap to Elevator compensation - Be prepared to apply down elevator when deploying flaps to level out the model - SAFE Select is only available as a momentary button with this model using this profile, hold the button for SAFE on and release for AS3X mode. For the best experience, we recommend flying with a DX6e transmitter (or higher) with this model"
Sorry, might be time to upgrade to a DX6e or something that is programmable.