I have to extend a surface of a solid hull upwards to form a bulwark and it needs to follow the same fair line as the hull to be seemless. ie, it needs to have the same curvature and profile shape. What do I use please? The bow has an inward tilt that could probably be done in 2 rail sweep, but the stern needs to follow the hull fairness up to half way forward.
if you are lucky ExtendSrf could work. otherwise it should not be so difficult either. you can either loft using the bottom edge of the existing surface plus the curve on top best if it would have the same amount of spans/cp´s the result should be along the outer curves you have marked up. or you can use sweep2.
if nothing of that sort works you have to post at least some parts of the geometry as a file.