How to deal with video projectors not supporting Surface's 3:2 aspect ratio ?

Hi, When connecting to a video projector in duplicate mode, the Surface monitor has to be set to a resolution with an aspect ratio of 16:9 because video projectors don't support 3:2. Is there any way to keep the Surface monitor at optimal resolution and aspect ratio while sending a resized 16:9 video to the projector, i.e. displaying black borders on the external monitor instead of the internal one ? Thanks