Not sure what you mean by "inbalance of 500kgs".
Speaking as an ex-AF dispatcher who used to regularly dispatch the A321,what I do know is that it is a pain in the bum to trim.Because it is basically a stretched A320,and the stretch was done forward of the wings,the extra pax weight in the front makes it very forward-heavy....our standard trim for this a/c was all bags in rear hold and block some seats out occasionally and this was usually enough to keep it in trim!
Hope this helps,
777.