Yup - the weight of the JPs and the quality (or lack of) of the rings were two worries I had when doing my AMC motor, having heard exactly what's been said here.
In that case, the 8.5:1 JPs at +20 weighed 23 grammes more than the originals at standard bore and 7 point something:1. Not a big difference in that case I didn't think, but not a perfect apples to apples comparison either. How much heavier is a JP for a B44 I wonder, just as matter of interest? Maybe it's a 'singles thing' . . .?
The rings didn't give me any problems either luckily, and 20K kilometres down the road, no reason for concern. To start with, I was definitely very edgy just waiting for trouble to strike. Now, I give it full beans through the gears just so I can hear the sound of a high-revving comparatively shortish-stroke twin with an amplifier for an exhaust.
So dunno - am I just lucky? Or are some versions of JPs better than others? Or does it come down to getting those bores sized spot-on to suit by people used to fitting the things, and just maybe helped by being ultra-careful for the first few hundred km on what was not only a new pistons/rebore/valves/guides/seats/cams/followers job, but also a brand new crank and forged rods . . . all of which cost a bloody lot of beer vouchers. (There were none left to make the cycle parts half as nice, but that's Ok.)