Best: Adaptive Gaussian block 11, C 5, no blur → ~half the hull breaks of old b21/C15. Then AutoTrace (corner 140, filter 4, error 0.5, line 0.5) on that mask — small gain.
Keep (alt): Adaptive mean b11/C5 (fewer breaks, thicker lines).
Superseded: Adaptive b21/C15 and default AutoTrace from round 1.
Drop: fixed threshold, channel separation, black-hat, Sauvola, Niblack, pre-blur, DeepSketch.
Wobble/doubles come from the mask, not AutoTrace; sails/logo need a crop. Tap image = mark; pinch/scroll = zoom (8× max); drag = pan; double-tap = 2.5×/fit. Marks save in this browser.