wouldn't be overly "fishy" , dual controls would be what...yoke and rudders? got both of those in a C90. If the guy is willing to give you some dual given in the C90 it wouldn't be a bad idea, also, it'll help you start building the multi time that you're going to need when you go to get a job later in life. Even if you can't log it, it'll be some good experience for you flying something that's pretty quick and turbine powered, several flights in it, and the systmes should start making a little sense.