Wow you are like the complete opposite of me. I can play the second movement easily now and I waited to play the Clair De Lune. I guess it isn't that I couldn't manage it but I am not to familiar yet with key signtures witrh more than 4 sharps or flats. It just gets a little confusing and it takes a little more time.As for why they are both at level 7 I really don't know. Adagio Cantabile seems to be a lot easier. The speed requied in the Clair de Lune is a little faster than that of Adagio Cantabile. The arpeggios make it more challenging as well as the key signature.And your plan sounds good to me. If you are working with lesson books make sure to stay consistent with those. Since you know that you worked up to that point you know that you can play those pieces. They will also help to develop your technique. If you are past books, then I would say make sure that you are staying consistent with "something" to delevop your technique. Your idea of working with one hard piece is something I do as well. Take a little bit at a time and before you know it that piece will be mastered.Hope I was of help