Everybody's idea of what is too heavy for pocket carry will differ,
mine has the Model 649 right at the top end of my "comfort limit."
Since I have other options, I do tend to go with
either my M38 Airweight or 638-3 for pocket carry.
I have tried carrying my M649-3 but find it just over the weight limit of what I find
comfortable for pocket carry, unless I'm carrying it in the pocket of a heavy jacket or coat.
When it come to square or round cut pocket holsters, it all depends on the bottom contour
of the pocket that you'll be carrying it in. I use both on an equal basis, depending on the pocket.
One last word on the Model 649, one of my favorite S&W's.
The Troopers of The Michigan State Police relied on them as
their back-up guns (BUGS) for many years, some still do.
The MSP duty pants have a special holster pocket sewn
inside the regular pocket(s) for BUG duty........
P.S.
For the record, the MIM parts arrived on the scene around 1996-97.