I have a 21sf & a 27. I see that space between the base plate and the grip in both guns. My wife won't shoot the 27 because she says the gap pinches her little finger. I use the Pearce +1 extension on the 27 when I shoot it as a 40s&w or 357sig. I use the Glock factory extended mags when I convert it to 9mm. I like the feel of the Glock extension better but it sticks out more when CCing. My wife says that it doesn't make any difference. They all pinch her pinky. Oh well, I guess she will stick with her Buck Mark.