Scaling UMG button by image

I’m working on my main UI, and I have images for each button state that are the exact size I want the button to be. However, when I set them in each style found in the Button>Appearance>Style menu in the button’s details, it doesn’t scale itself. Size To Content only seems to work for widget children of the button, not for its own images, is there something obvious I’m missing here? I can make do by manually cut & pasting the Size X and Size Y from the image to the canvas slot, but that seems like a really cumbersome solution.