B-Roll doesnt keep correct aspect ratio

I record all my clips in 2.59:1 aspect ratio, with the black bars on top and bottom. When I start a project and enter a clip into the timeline the aspect ratio and bars are correct - until I use them [clips] as B-roll. When the clip is used as B-roll the aspect ratio and black bars are gone. The clip is automatically zoomed in to take up the whole screen. The end result is inconsistent aspect ratio throughout the video project.

The Jacob about iMovie, v2.2.3