That's odd. Can you share?
I recommend using the standard 1024x768 document size. Hype will make sure that a 2X image is loaded for retina devices if you provide a large enough image. That's only if images provided are large enough; Hype won't create a larger image starting from a smaller one.
What might be part of the file size is the generated Default.png file for such a large document size. If you rename your .wdgt file to be a .zip file, you can then unzip it and take a peek inside.