I used clear edge grain Douglas-fir 3/4" thick, boards from a local lumber yard in building my KR2. Have to be sure it meets specs in grain run-nout, no knots, etc.
For the longerons I planed it to 5/8" thickness (left the height at 3/4", dampened the longerons and bent gradually over several days in assembling/shaping the fuselog: no cracks/splits. Laminated the spars ;do not want to cut spars from thicker pieces due to possible hidden pitch pockets. About 15% heavier and stronger than sitka spruce, a little over build/safety facter.
