I updated the original design by rcexplorer for 12.7mm square (close to 1/2" square) wood boom/arms available in US. The notch to hold the arms in place does not work, so I removed it from my previous version. The large surface area seems to hold the arms in place due to friction. The added comments will help you to modify the OpenScad file. Added APM 2.5 mount holes. I am planning to add counter sink holes for APM 2.5 mount points. NOTE: This is a work in progress. I updated the original design by rcexplorer for 12.7mm square (close to 1/2" square) wood boom/arms available in US. The notch has been removed from the design as it does not seem to work. The extra surface area seems sufficient to hold the arms in place. The added comments will help you to modify the OpenScad file. Added APM 2.5 mount holes.