A freind is giving me a surface planer and he said it pobably needs new knives. There's a couple of nicks that will cause raised lines on the finished piece. Then I started thinking, what if you made two large raised portions on the top of the core? How would that effect flex? This could be done with a molding planer or by filing the profile into some beat knives.
It would add stiffness lengthwise, but probably not affect torsional rigidity much. It would also add some weight unless you made the rest thinner - but then you would have more twisting issues.
You could do that, make it thin and add glass or CF to control your flexing properties
I used to be a lifeguard, but some blue kid got me fired.