I have also received an email from Les, and will attempt to explain his reason for the lock change in laymens terms.
He states that the basis for most lock strengths is the three points of the triangle formed by the pivot, the stop pin, and the contact point where the lock engages the blade. By moving the contact point further from the pivot point, they have increased the size of the triangle, and thus the stability of the lockup. Les also stated that the position of the stop pin has been moved further back from the pivot, for the same reason.
He also stated
Much of the additional material did not contribute to the stability of the lock but actually caused the locks in some units to be prone to wobble because the actual point of contact was too close to the pivot pin.
I took the liberty of disassembling one of my Sebenzas, and found that the contact point extends the entire length of the cutout, and not on any one point along that expanse. The same holds true of the Darrel Ralph Apogee that I own. I have not done this to my pre-production Pinnacle, as it would void the warranty, but from Les statement it appears that this would not be the case on the Benchmade Mono-lock. If such were the case, there would be no reason to move the contact point further out, as it would extend all the way to the edge of the handle, as far from the pivot as is possible.
I sent a reply to Les thanking him for the clarification and for explaining the reasons behind the design change. I also asked if he could clarify his companies future plans for the Pinnacle and the Mono-lock, as this part of my post was not addressed in his email. I hope to hear back from him in this regards, and will let you know what, if any, plans exist.
And Roy, I agree that the lack of continual use of the mono-lock is a business decision, based on the practicality and popularity of the Axis Lock. But with less than a year in the field, the Axis is certainly not a proven design. The recent threads regarding the increased play in the blade of the Axis might be a portent of things to come. I was perhaps harsh in my assessment that BM failed in their attempts to produce an Integral Lock design, but I will stick to the caveat that any good experiment can be repeated. If they drop the use of this style of lock because it is not a practical or economical design for them to use, then the Pinnacle experiment has, indeed, failed.
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James