How to set the Display aspect ratio to 16:9 explicitly when using a VGA adaptor

**Background** I was presenting at a venue where the projector supports 1280x720px resolution (16:9) via VGA cable (I've previously used the same room and equipment on an older 2011 MacBook Pro running Mavericks). Yesterday I used a newer 2014 MacBook Pro Retina running Yosemite, and was unable to set this resolution - the closest I could choose was 1280x1024px. When the MacBook is mirroring to a projector via VGA cable, the *> System Preferences > Display*s panel looks something like this: In my case the only options were 1280x1024px and 800x600px (this image is from the web - I didn't get a screenshot at the time). **My question** Is there anywhere, other than the *> System Preferences > Displays* dialog, where you can explicitly set/force the output resolution? My only options were 1280x1024 or 800x600, yet I'm positive the projector supported 16:9 since I've used it before.