Rare Item Drop Odds

Does anyone know a way to modify the odds of a rare item dropping without expanding the monster data?  Is it possible?  I know the program ff6exped exists that expands the monster drop list and can change the odds, but I don't really want to expand the data this late in my testing phase and potentially break the mod with real hardware (which is a huge priority of mine).  I was hoping there would be a simple hack to modify the odds of one or two monster/item drops.