“…In order to overcome the inherited downsides of the above-mentioned semi-hodograph transformation and to allow for stagnation points and critical layers, many papers use a "naive" flattening transform, where on each vertical ray the vertical coordinate is scaled to a constant; see [1,21,23,24,31,35,37,47,50]. Consequently, a drawback of this naive flattening is that it needs the surface profile to be a graph and can thus not allow for overhanging waves.…”