Here's some information I posted on here a few years ago
I have one of each in the garage and just measured the weights on them. The 50 oz weight is approx. 140 mm long and the 28 oz one is approx 100 mm long. Visually easy to distinguish. Hope this helps.
I had to trawl through my posts to find it as i don't have the flexplates in question any more.
Both of the plates I had, and every one I have seen, just had a weight and no cut out opposite. There are plenty of websites showing both side by side without cutouts. I would think that one with a cutout is probably a 28 ounce one that's been rebalanced to 50.