Well, I basically thought that if you are working in a widescreen project in VisionLab then it will be widescreen when you render it no matter what. I was working on a logo that was full screen but needed to go into a widescreen movie, I imported the fullscreen video into VisionLab, I set it to know that the video was fullscreen so it wouldn't get stretched and have an aspect ratio problem, and I made it bigger so there would be no pillarbox in the widescreen frame (so I essentially converted the fullscreen video to widescreen).
After I was done with the logo, I rendered it and, even though the VisionLab project
was widescreen, the video still came out fullscreen. The reason for this is that VisionLab won't convert the imported video itself: it'll render the video in whatever aspect ratio it was in the first place. So you should always import a video into a project with the correct aspect ratio, or be ready to unsquoosh the video in your editor if you do what I did.