Adjust layout preview scaling for 4x6 and 2x6

The current layout preview scaling makes no sense. Right now, 4x6 and 2x6 options are set to the same width, making the 4x6 preview look smaller than the 2x6 strip. This confuses customers choosing their print size.

Please fix the UI to scale layouts by height so the 4x6 displays at its realistic, larger size—same height as the 2x6, but wider.

Thanks!