I'm not sure what you're doing exactly and why, but are you sure you want to do this? Do you know exactly what your viewing devices will be? Otherwise, with a fixed aspect ratio, how can you be sure that your project "takes up the full page"? The browser may be resized to a different aspect ratio or using a mobile device with a different aspect ratio.
It sounds like a bad idea to me, but that may be just because I didn't get what you're trying to achieve