Thanks to Jenn from Canada for her email. You might want to try her bobby pin/kirby grip method.
Just wanted to say thank you for making a great idea happen! I’m not an amputee but a quadriplegic. Getting my own hair pulled into a pony tail is next to impossible. For years I’ve had short hair and it wasn’t an issue, but in the last year or so I’ve been growing it out. Pulling it up wasn’t much of an issue until the summer heat. One day I was thinking there’s got to be a way to do this. I came up with an idea like yours and thought someone has got to have come up with a way to solve this. I Googled and found your site, was excited and ordered that day.
The way that works best for me is the 2 handed method (even though my hands don’t work). I found I wasn’t able to wrap the strings tight enough to keep them in place, so I added ‘bobby pins’ to the ends at the knots. After I wrap the strings I stick them in my hair and they stay in place.
Sorry that’s a bit long, but really just wanted to let you know how you added something else to my independence. 
If you are using the 1-up a different way, drop me an email or comment on the blog and share your story.
Tip! A Topsy Tail tool works well with the 1-UP. (I just found the one I had from years back and gave it a go.) Buy one, or make your own and add another hair style to your repertoire. Checkout this blog for details. http://www.cutegirlshairstyles.com/tips-and-tricks/tips-tricks-how-to-make-a-topsy-tail-tool/