Hi guys.
In all the battleworn khukuris I have had the pleasure to see and handle I have never seen a modification other than what type of fabric they slipped over the scabbards. No holes drilled, no cutting into the original wood. I do have one bizarre modification that someone turned the knife into a "left handed" model by reversing the frog and screwing it into the bare wood. I have a picture of it but don't know how to post it.
The Gurkha soldiers were issued a parade knife (patent leather and highly polished and sharpened blades) and a fighting knife. There were regulations stating how and where they wore it, but in combat pretty much anything was allowed. The current Gurkhas (of England) and Gorkhas (of India)have the same setup, but their combat knives are heavily camouflaged including painting the grips green, brown and black.
Civilian knives are a whole other deal. I have seen them with straps and buttons, extra knives and tools stuck in the back, homemade frogs, pieces of ivory and bone with incantations engraved on them, wrapped with wire and coins....it goes on.
------------------
JP