Not a race board I have one of those I want a more traditional surf board but fast
Great to see your into another project!!!
What I've heard is that fast boards are stiff and have no rocker. You might find some inspiration from the chat here. these guys use modified twin tips but the speed focus is what might spark some ideas.
They also mention about emulating 'shark skin' for its low friction properties. I have heard that sanding the underside of a board with really fine sand paper results in a very fine layer of turbulent flow being created under the board and this reduces friction.
What specifically have you got in mind for the board?
... also, your Q about concave. I have heard that concave in surfbaords gives directional stability. The long length over which the concave can extend means that the concave section can act like big distributed fins. A friend who loved riding old surfbaords had one with about 10mm concave over about 1/2 the length of the board and said he struggled to turn it and had to work hard to actually surf it because it just wanted to point down wind all the time.