Hello Mark,
Thank you for your post.
In the Viewer interface you can set
scaling (see options
on the toolbar - Normal, Stretch etc.) that is you can shrink the remote image to fit the bounds of your Viewer monitor. However, if you want to change the very resolution of the remote screen you will have to do that on the remote desktop itself, that is by accessing the Windows "Display settings" menu.
In the future though we might add an option to change the remote screen resolution from within the Viewer.