Excellent point IBA. I'm guessing since the checklist cards are official magic cards, having a checklist with the dual lands on it won't be tournament legal. But the question needs to be asked to WotC. The checklist card is a proxy.

Are you going to have to show proof that you own the double-faced cards before a tourney? What if you "borrowed" them from a friend, but your friend decided to use his physical copies? Are your checklist cards not valid anymore?