Gutenberg gallery image sizes

Hey, I wonder if there is a way to set the size of the last images that appears in the gutenberg built in gallery block? This in case for example that there is an uneven number of photos and the very last row will only have one photo instead of six and this final photo will display large size to fill the width of the gallery instead of showing small size as the other photos in the rest of he gallery….
Any ideas how to change the size of this last photos to fit and have the same size as the rest of the gallery?