Virtually all of the domestic refrigerators I have looked at with the intent of using one to store photo materials and specifically colour products seem to conform to an approximate footprint of 60x60cm. Once the internal dimensions are estimated, these dimensions are not compatible with storing 20"x24" RA- 4 paper for example; and so is storing vertically paper a sensible proposition? My major concern being consistency and material stability.
Tom, I had some 8x10 (monochrome) paper stored on edge rather than flat. It developed a curl which is a pain if you develop in trays. Paper of the same type stored flat wasn't curled, so these days I make sure that all of my paper is stored flat.