Personally, I would find it a bit floppy for face lathering, (I like to set them aroung 45mm). A couple suggestions:
1. Talk to Tony. There is a certain amount of variability among the knots, and he is usually willing to pick out one that is the closest to what you need.
2. Have you considered trying to grind down the shelf with a dremmel, rather than cut through it? That might work with less risk of breaking the handle.
3. The finest is a wonderful knot, but for extra backbone have you considered the black badger? It is a bit more scritchy, but not bad, and is very dense and strong.
When we remember we are all mad, the mysteries disappear and life stands explained. - Mark Twain