I am looking to mount a red dot on my fnx40, probably a Burris ff3 due to my financial status. Ideally I want it to look like the fnx45 tactical. I have a friend capable and willing to do the milling required. I understand that I most likely won't be able to use the stock sights anymore but I can deal with that. My questions at this point are, has anyone done this? Do I only need to mill down enough to recess the sight where I want it in the slide or do I need to do as the 45t is and mill a big opening and use a mounting plate? Any information or ideas anyone wants to give me would be greatly appreciated.