1. Thanks to /u/soulcatcher, there seems to be a magic number of 242 image asset slots (box art, thumbs, save states).
2. The original 30 games use up 106 of those 242 slots (60 for box art and thumbs, and 46 for pixel art and other hidden items).
3. If you were to hide the original 30 games and re-add as new ROMs, this would free up 46 image asset slots, but you would also lose screensaver pixel art.
4. What people mean by keeping 44 is that only 44 thumbnails are displayed on the home screen. Therefore, if you were to delete the ones that wrap around the sides (and are thus hidden), you would be freeing up more of those image asset slots. To do this, you go to the game folders (in your hakchi2 directory) of those specific games that have hidden thumbs on the home screen and individually delete the smaller of the two image files in that folder.
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Ooh this is exciting. Unable to test right now either, but can't wait to do it!