He is using hockey goalie helmet face mask screws in this post. I have tried this and it worked pretty well in my new ATA helmet. I used 4 screws and posts per eye though instead of 2 per eye.
http://www.whitearmor.net/forum/topic/28633-howto-ata-helmet-build-hand-painted-details-pic-heavy/?hl=%2Battaching+%2Blenses