Just wanted to share a board Brian Himlan -- aka longshipdesign -- just finished up for me.
The idea was to take a classic stubby template and pull it out to 9'1". About 4.5" of rocker in the nose, a little over 1.5" in the tail drawn out very slowly from the apex. So far very pleased with the results. Speed is king with this board for sure - get into the pocket, set it and forget it!
One of the obvious reasons (at least to hull riders) round rails can generate so much speed relates to their natural placement on the wave face. The lateral drag of the rail pulls the board up the face, into the part of the wave where more water is moving.
Two shots of the same rider illustrate this point. Round rails up top, down rails at the bottom.