In our testing we found that the standard Google Cardboard design lets in too much light, and is a poor fit for many different shapes of nose and forehead.
To solve this, we created this optional add-on. Just print out this file as a template for cutting neoprene or foam with a pair of scissors. We do not recommend using a laser cutter as this can be a health-hazard if you select the wrong materials!
Next, take a simple clip-tie and thread it through the holes as though you were sewing...
Don't pull it too tight. The tighter you pull it, the more extreme the shape will become.
Grab a glue-gun and just press the shape into position.
This is a perfectly good design to hold with both hands. This can actually be more comfortable and reduce motion sickness for many people who use VR.
If you like, you can glue some extra head straps to hold the headset in place...