Hey Roger! The DD2 has a fuller rail, less tail and nose rocker and different bottom curves. This makes it faster and holds rail longer, whereas the Happy Everyday has more response in the pocket and pivot.
CI and Dane have designed the Dane DD2 Fins to match this board. It is a full glass fin with the same AM sides with a smaller back fin. You can view them here: www.onboardstore.com.au/shop/accessories/detail.php?id=25406&shop=accessories