DIY Outdoor Aviary - What Aperture size mesh?

[MaltSTi]

Hi

Im planning to build a large outdoor 'cage/aviary' for our Alexandrine. He (or she) is about 15 months old.

What would be the minimum size aperture mesh you would recommend for a parrot this size?

Any tips/tricks/pics of anything anyone else has done themselves before?

Any help or advice is much appreciated!

Thanks

Matt