Anyone know what roll coupling, or rudder roll coupling is? I know what it but I don't know how correct it or what causes it. If I knew what caused it I might correct it. I have read people say they mix it out, but I don't know what to mix or how to mix it to get rid of it. Thanks for any help...

Do you mean "aileron differential" ?

No, Roll coupling is when you do a knife edge to the left and the plane roll's toward the conapy and turns to the right.

or to the left,

if the plane rolls when rudder is applied, make a mix that has rudder as the master and aileron as the slave. The goal is for the radio to add the approperate aileron when you apply rudder so that the plane stays in knife edge. usually you mix right roll with left rudder, and vice versa. Start out with about 2 percent and then adjust from there