Lot more experience here than what I have but I do not like 357 in an ultra light weight J frame thinking of the Smith scandiums. Next frame size up is not so bad but those 11 to 12 ouncers are most unpleasant and I'm being kind. Don't get me wrong it is impressive that they can make a handgun that is that light let alone in a magnum but in my opinion for me it is just too much. You might take a look at the new K frame Night Guard line Smith just came out with although I do not know the weight off hand. Air weights in 38 special at 15 to 16 oz. are not bad and about as light as most of us mortals care to go.
If you really think the scandium light weight mag is the way to go I'd strongly urge you to find a way to test one out before you buy since they are pricey. Punishment is supposed to be delivered on the business end of the barrel not both ends. Just my opinion tho.