TriCopter base for US

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.

1. Edit the OpenScad file to change the width of the wood