Oops...my apologies! I got a few responses to my earlier post about the wheel on the canopy of the Tamiya Betty. It was the perspective of the drawing in the instructions that fooled me. It looked like it should mount on the side of the canopy--obviously not possible. I figured it out a few minutes ago--just before Ashley responded to the post with the solution.
The wheel mounts in the center frame of the canopy above the pilots' heads; Ashley said it is a rudder trim wheel.
Thanks to all for your responses.
Bob