alexanderkrizak asked: If the as-fan of double-face cards is 1.125, that means that one out of every eight packs has a second double-face card. That makes sense because you already had the technology to make one out of every eight packs have something different; that's the same ratio that mythic rares have. So I suppose the final question is, does the second DFC replace an uncommon or a common when it happens?

The first double-faced card is a common or uncommon and it replaces a common. One in eight boosters gets a second double-faced card which is a rare or mythic rare and I believe that replaces an uncommon.