I am wondering if there's an easy way to change the size of the image in the upload zone without having to create multiple products. For example, I have a fixed background but I would like the upload zone to either be portrait (08x12) or landscape (12x08). Is it possible to hide one of the two layers then have the user select in the main bar one or the other to display?
Yes, you can create a png overlay with a transparent part exactly where you like the image to be inserted for each direction (landscape and portrait).
Those overlays can be loaded into the canvas via the "design" modul.
In order for this to work you need to enable "per pixel detection" in the general settings of fancy product designer so the customer can still drag his or her uploaded image within the canvas.