Hang tight on any committments related to adjusting the confluence of the decking at an angle, particularly if it is treated lumber. I have done decks with similar features, laid them in perfectly, and come back the next year and found them looking very similar to your complaint. The wood shrinks at different rates on each edge, presumably due to the different overall length. By the time you are comfortable that it won't move or shrink anymore, your self-critcism will be long gone and you likely won't worry so much about such a minor detail.
