I have carried snub j-frames (a 642 and a 640) with good results for a few summers, so I feel ok leaving some comment (though my body type doesn't match yours exactly, I'm 5'10" and 160).

For on belt carry, you may find that having your holster made with extra length might help stabilize the gun and keep the grip from printing as much (snubs have a short barrel and grip may tend to flop out). I went with a steel J frame mostly when I had a belt because the extra weight was not a big deal on a good belt. I was able to conceal and carry comfortably, but every time I go to the trouble of putting on a belt, I want to put on a bigger gun. This was a personal choice for me, and not necessarily a knock against this config.

For quick errands (or whatever) with no belt, I have become a fan of Dark Star Gear's casual carry AIWB (there's a thread over at PT forums about this config). With an airweight, this seems just the right weight to conceal without pulling pants down, and is quick on and off. Was a good match to what I wanted for the snub airweight role. I was able to conceal and carry comfortably in T-shirt and shorts.

I know Tom over at DSG can make holsters with extra length if you need it.

Any reason you don't just pick up a no-lock 642/442 (which are plentiful right now)? No hammer to snag on draw or print while concealing.