I just figured it out. For those who have the same situation, here's what you do...very simple: Place your additional images in your images folder as usual, with the underscore then identifier, for example, say your main image is tShirt.jpg, your additional image will be called tShirt_ladies.jpg. The Ladies T-Shirt will be the additional image that comes up on your product page, however it won't watermark on the large image unless you place a tShirt_ladies_LRG.jpg in the images>large folder.

I woke up this morning with the revelation, and by golly, it works!