Before you take any action, I suggest that you ask at least other shooters, preferably ones who shoot well, to try your P99. The fact that it shoots eight inches low may be you and not your gun. As far as contrasting rear dots, I prefer yellow if I can get them easily, but am happy with an all-green setup. And, the fact that the rear sight seems to move a bit is fine. All of my P99s do this.