You said it doesn't integer scale 3x, it does. You THINK that you have to set it up to custom, you do NOT. You choose ratio from the core, then set up the viewport to 960 x 720 and the integer scale to 3, and BOOM, my 720p TV has black bars on the top and bottom. You said this is impossible, I'm showing you that it isn't, and the core provided ratio IS the actual ratio, so why is that wrong? The image is 3x the original size and is 768 x 672, or (256x3) X (224x3). This is exactly what you were complaining you couldn't do, and I did it.
You must be setting the viewports to two different scales, and that's not what you do, or you will get the skewed results you are getting.