I have encountered challenges in planing and sanding adjacent wood species of different densities while shaping and finishing wooden surfboards. For example, on a recent board made primarily of balsa with redwood stringers, the much less dense balsa is so easily removed that the foil or overall flow of the board contours (particularly edges) can end up flattened or otherwise distorted.
The only property I’ve found listed for wood species is specific gravity, or the density compared to water. Is specific gravity an appropriate proxy for shear strength? If so, my next board will be a combination of paulownia (.32) and parota (.34). I realize that grain orientation and tightness determine the working characteristics of a wood surface, something I can contour visually.