Sorry to dig up an older thread, I am interested in the Palm Swell grips for my 4566TSW, after calling S&W this morning they said they would leave a gap, as they were designed for the frame mounted decocker. I picked up a set of arched grips listed for the 4506 on Gunbroker, but I think they may be the same way as it doesn't have the 90 degree corner in the front upper left side of the grip. Interested in the palm swells as the my newer arched ones, although better than the factory staight, still feel a tad thin.