Lots of food for thought, though I have tried a few ways for my Becker BK11 and I have found a few that worked with an aid for security.
The one I liked the best had a strap with a snap for retention, but had a grommet up against the foremost section of the finger choil on the blade, and a screwed post that would thread the grommet and act as a mechanical stop pin for the choil and blade.
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The idea was given to me by a nameless Busse sheath that I had seen. They used the Talon hole for the retention point.
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The above is not my work, below is.
If you know who made the sheath down above, please let me know. I would love to give credit.
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Another option would be to do one piece front panel and just fold it back and stitch that down. This would eliminate all of the front strap and securing needs, while allowing for a larger canvas for your art.
Becker BK11 sheath I did along with all of the blade and handle work.
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Thanks for the compliments on my EDC sheath. It means quite a bit coming from someone as skilled as you are.