How to enlarge the Navigator window?

Maybe this image will illustrate what I am wanting to do.

I shot 30-40 images of this squirrel at the top of a stump. In some, his tail was behind the stump and visible in others. I zoomed in to 1:2 for this example, but it might be 1:1 at times. This lets me see if the eye and whiskers are sharp, but when zoomed in, it can't tell if the tail is visible except in the small navigator window. I don't see any way of enlarging the navigator window?

I am possibly going about this wrong, too? Is it possible to do a split screen on the same image? Instead of two different images (as above), can I view one side at 1:1 and the other "fit" on the same image? If so, I would need to advance to the next image after assigning an X, P, or U, and see it in both zoom views of the next image.

Any advice would be appreciated. MJ