Been watching videos lately but never seen one of his boards in person. He shows up to 1 1/8 inch deep concave using straight edge but then demonstrates that if hold straight edge at 45 degrees to long axis, "it is dead flat". BUT when he does that demo, the ends of the straight edge are inset several inches from the edges of the concave. Am I correct then that these are more curved sided channels with flat bottom i.e. all the curvature concentrated in outer couple inches rather than curve distributed across an arc?
Start at 00:45 for visual