Masking GameObject in Canvas

Now, I've found that this question crops up in several places, and the answer is never accepted or is some half-working wish-wash way of doing things. I need to mask several GameObjects that are in a UI ScrollRect. These GameObjects are also animated, have several different sprites, and resize on the go. Thus, due to the additional resizing aspect ratio nature of textured GameObjects, I cannot RenderToTexture, nor would it be optimal for obvious performance reasons. So I'll ask the question that many have asked, but for a more complicated situation. How do I mask a GameObject as if it were a UI element?