I finally got around to making my mantis clone. You can see I permitted myself a little artistic creativity. Now this is only the prototype, which I ground out of heavy duty band saw. It's really rough, but I wanted to see how useful it would be.. test out the principle.

Honestly I have to admit, I'm a little disappointed. I believe my steel was a little too thin (40 mil), the tension tool tends to move around a little too much. The looseness of it makes it hard to use, especially one-handed. If I can get my hands on some 50 to 55 mil I might give it another try.
In the meantime, I'm not too sure I want to spend for a tool, that might not be too great, when an Allen key does the trick better.