I’ve used quite a few of the plastic Magpul sights and have never seen one flop from side to side. I have seen a few metal sights do that over the years, one being a YHM the other. PRI.

That said, for a red dot equipped gun or irons only I like the Daniel Defense A1.5 fixed rear sights.
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Fixed carry handles just add too much weight and the handle is smaller that the A1 or A2 so they ain’t even a comfortable way to carry for me.