Used some 3/4" thick x 2-1/4" wide solid hardwood flooring to fabricate two 4' support beams. Each one was made by squaring up two planks back to back, screwing them togehter and routing off the tongues. Will make a couple of 5' versions the same way.
One end of beam under trailing edge should be even with top of rudder with 3/4" spacer placed under beam at the bottom to achieve proper geometry for drilling and assembly.