You need to step back a little with your SU camera and then
click the "show render area" from the MXW plugin. You'll probably
see two greyed bars appear on your screen. They are either on both sides
of the screen on at bottom and top.
Now make a new SU scene (e.g. scene 1) from this view. Export to MXW.
You'll find the scene as a camera with the name scene 1 with the exact
position as the SU camera.

Hope this helps!
Greetz
Dennis

btw I'm on a Mac too…