Thanks for posting the page and in theory it looks like it will work, but I tried it back when this was published and soon found out that it didn't hold the horn that secure. You still had too much horn covered and last, you are limited in movement, as you have to keep the strap tight!
I think that is why a Horners Spike works better and it is solid and leaves both hands and feet free. Just take about a two foot 2x2 and round the corners, shape one end into a blunt point and clamp the other end into a sturdy bench vise. Wrap the pointed end with some damp leather and just push your horn on!...wallah! The horn is solid and you only have to loosen the clamps of the vise and adjust and/or turn the horn to any angle you need!....Your hands are free, the horn is completely open and no leg cramps too!
Rick