Is it supposed to be literally a "half link"? 'Cuz when you look at how the link plates alternate, between "inner" and "outer", there's obviously an "extra" plate in there. I wonder if that also accounts for how loose the chain appears. IOW, take out that half link, re-assemble with the regular outer-inner plate sequence, and remove the slack in the process. Does that make sense? Should anything chain-driven have that much slack?