I am assuming that you are a Police Officer as you have used the term, "Duty Knife."
There are a couple of issues to discuss really.
Are you right or left handed? If you wish to maximize the potential of a Defensive Knife and you are carrying a Handgun, you really need to have the knife on the other side of your body so that when everything goes wrong and you have three toads on you fighting you for that Pistol, you have something else to give them for a present.
Most friends of mine that are Police Officers, the Commander will not work strong side because the Duty Holster is in the way and if they could get it out fast, they would probably slice the leather up, etc.
I know that your belt is probably already crowded a bit, but have you considered putting a folder in your off side pants pocket and then putting the Benchmade in a Folder Sheath on your Duty Belt?
I draw a very strict, unbending line between Utility and Defensive Weapons.
I think the knife you carry to aid you in retaining the firearm must be as sharp as it can possibly be, period. No debate there. It has to be, nothing else will suffice when you need it.
That is just a start, we need to have an active exchange involving how tough the material is on your Uniform, because the Wave Opening on the Commander can be absolute hell on some material, etc.
Like I said, this is a start.