You may be on the wrong track, here. The 642 is a gun that is designed to be carried comfortably all day. If you are not going to carry this gun, I would recommend a larger frame revolver. They are easier to shoot accurately,
and can absorb recoil much better than an Airweight snubby.
I carry an Airweight snubby. But for home defense I reach for a larger, steel frame revolver. If you go to
Home Page - Smith & Wesson they have a Handgun Selection Guide on the left hand side. Go on that and then go to Personal Protection. Look under Home/Business Defense. The guns there are all heftier than the 642.
I do not want to rain on your parade, but snubbies are really not all that easy to hit with. They have a short barrel and the distance between the front and rear sights is limited, so they are harder to aim. Also, the 642 does not have a hammer that you can cock. You have to run the trigger through a complete double action stroke, and the trigger springs on these are a bit stiff. A medium frame revolver will be easier to hit with, especially if you are not a dedicated shooter who practices a lot.
I encourage you to pursue this quest. I would like everybody to have a gun in the home. But an Airweight is a compromise of size and weight vs. ease of shooting and felt recoil. You should consider a larger gun.