I'm working on swapping the thumb safety on my Colt New Agent with a Wilson Combat Extended version (brownells #965-600-007) and I cannot get it to engage on safe. I had to fit the post by sanding it for hours and I'm not sure if there is something else I might have to do. I can insert it without too much effort now but it will not slide up to the point where the angle goes into the notch in the slide. I've also visually compared it to the stock one and there is a slight grove cut out on the base of the safety rod so I matched it by using a very small precision file. I'm in no rush to get this done as it's just a little project I'm trying to take on myself and I enjoy working on things. I'm not above taking it to a gunsmith but just looking for some advice for someone who might have run into this. Any help out there? I'll post some pictures later.