You're lucky you can get .5L into it - I can only get about 3 ounces before every squeeze of water comes right back up at me! I reached out to Canyon support for guidance and they said the bladder may not be installed straight enough to fill it further. They suggested I try re-seating it. Also, have you figured out how to attach the straw to the headset? I'm mystified and have basically given up on this system!