On the Royal Evo/Pro/Sx you can cheat by making a mixer and then assigning it to those channels and using the mixer curve to make some adjustments, not sure if the MC4000 works the same way though.
E.G on a friends FW190 we assigned the tailwheel steering to channel 13 and then made a mixer for the tailwheel steering, with rudder and fixed as the inputs, the rudder is only active when the wheel is deployed and travel is set at the mixer, the fixed is used to trim the tailwheel.