I'll be honest here, aside from I believe about 1 track (the ice berg peak one), I never really liked the music added to sky. Not as much as I like the original songs.
But fortunately, this particular source isn't so bad, and I like this mix a lot. It certainly is conservative, but it's still good. I was going to comment mostly on arrangement this post, but all I can say is that it's very solid.
The string, flute, pretty much everything sound very good together. The original parts are very cool, how you mix up both of leads - I love that. Speeding up things was a good call.
The percussion could use a bit of work, though. It might either be because it's soft or maybe it's a little repetitive, I don't know. It just doesn't sound like it's helping out the mix that much, though. Try humanizing it a little more.
Very good job on this!