Animation Assistant and image zoom

When using the Animation Assistant, I’ve discovered that the smallest zoom size, meant to show the entire image, causes 1 pixel to show the background around the entire image. I have created photos at a 16:9 ratio and 2500 pixels on the long side so that I have room to zoom into them. The Animation Assistant sizes them at 77% at the smallest size. Because I am using a white background in the slideshow, I can see a 1 pixel white border around each image if I use a Cut transition. I’ve had to change each photo to 78% to avoid this. Although the white background is not visible when I use a transition other than Cut, it would be preferable for all images to fill or slightly overlap the stage borders to avoid this manual adjustment.