Without the hammer shroud, only a bobbed hammer, the S&W Wyatt Deep Cover 637 that I have is smaller than a 642 . It is also an ultralight.
However, I never carry a gun in my clothing and am frustrated by concealed carry garment offerings that inevitably include all sorts of construction and cost for carry weight. Just give me oversized camp shirts in long or short sleeves. For me, guns belong on my belt on in a shoulder holster. My 637 is actually carried either in my go bag or by use of the clip grip in my pajama waistband.