I don't yet have my NMSFNO, but I assume the one thing I won't like will be this thumb "Trough".
The one on my HR fits and feels fine. But, the one on the HR is longer and shallower with a much less pronounced peak at the ramp. Longer and shallower is more versatile. Narrow and deep is less versatile and will fit less people. I don't know that I am optimistic about it feeling right. We'll see.
Some thumb indexing (ramps and troughs) feel pretty good and help give a secure grip. But, I find that unless I shape it myself, about 9 times out of 10 the factory or maker's ramps and troughs don't quite work so well for me.
I have had bad luck with most of the Busse and kin ramps and troughs. Most don't fit and feel as I would prefer. I could write out a long list of Busse and kin blades I have had to let go because I didn't want to hassle with modifying a ramp or trough that didn't feel right in my hand.
The ramp on my SJTAC was one of the worst as my thumb naturally fell on the peak of the ramp. It felt horrible to me and almost ruined a potentially AWESOME knife for me. But, I ground the ramp off and shaped it to fit my hand and now my modified SJTAC is one of my favorite Busse knives. I don't have a readily available pic of my modified SJTAC. Sorry.
The Swamp Rat HRLM had a thumb "Trough" that didn't work well for me. I modified the ramp and now the modified HRLM is one of my favorite Swamp Rat knives.
*** Unfortunately, these modifications somewhat require stripping the blades. Once again, I wish Busse would provide satin finishes at reasonable prices. These modifications, stripping and satin finishing blades is a LOT of work.
Adding steel where there is none is not very easy. The only realistic option is to remove steel if needed
Here is an option for what can "Possibly" be done with the NMSFNO:
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