My thanks to Kiarnan over at Reddit for this idea https://imgur.com/gallery/JfLTn
His bobby pin idea worked just as well with a couple of ‘O-rings’ such as I usually use in my own head torch mod Setting up the torch on the peak of your cap has the advantage of preventing the reflection on your glasses you get from mine, so it is better in some ways, providing you wear a hat!
And added a bare gram to the weight of the torch.
See Also:
http://www.theultralighthiker.com/11-gram-rechargeable-head-torch/
http://www.theultralighthiker.com/60-diy-ultralight-hiker-ideas/