G’day Chris, Barry and hopefully still Stephen,
Craig was my design and article so time permitting I should be able to answer queries on its construction.
Chris, once I had the basic deckhouse “wrap” I marked the highest point at the front of the wheelhouse, joined it in a smooth curve to the rear of the superstructure as per the plan, cut oversize and then carefully sanded to fit. As Barry suggests, you could use a cardboard template first. Take your time, a poor fit will detract from the model. It is a smooth natural curve, so should not be too difficult to match. Hope this helps.
John.