I generally practice at ten meters, and as I understand the terminology, what I do is less "Double-tap" and more "Controlled two". In shooting once, and shooting again as quickly as I can line up the front sight, I am usually putting both of them in the ten ring about half of the time. The rest of the time, the second shot is just outside the ten ring.
As I have read, in a literal 'double-tap', you shoot again as fast as possible. To me, this means, you are prepping the trigger as you recover from recoil to fire as soon as your muzzle is back down in front of the target. I have never felt like I can do this safely and accurately.
What I HAVE done, is switch out the slide on my Kimber to shoot .22s, and I can do this much more quickly than I can with a .45. What this means, is that in doing more dry-fire practice, one can learn the feel of the trigger better and anticipate better the correct timing for squeezing rapid shots. I read an article with Todd Jarrett, when he first decided to seriously compete, he started dry-firing. He fired over a million times. Click, all day long. In ingraining the exact feel of the trigger breaking, it becomes subconscious. You worry less about timing and more about the front sight. (He also confrimed that with modern 1911s, with inertial firing pins, you aren't going to hurt them by dry-firing them.) Todd Jarrett can shoot the el Presidente in 3.7 seconds. I am only an egg, as Heinlein would say.
I would do this more, but my wife frowns upon me clicking my cleared pistol at the TV all night.