Some rudder discussion here:
viewtopic.php?f=3&t=66I think both Ron Bowman and Kevin started with basically solid wood rudders. I know Kevin has changed to a composite, not sure about Ron.
Solid wood can work, just choose a moderate density wood (fir, mahogany or similar), don't get too aggressive with the section (say, a 10" chord with a 63013a shape), and make sure your tiller is grabbing the entire top of the blade, not just the front couple inches.