One other suggestion I would make - order a pair of two-piece clamp-on shaft collars from
McMaster-Carr (search for "shaft collars" and click on the links that come up) with an inner diameter that matches the outer diameter of the sway bar you're using.
Place them around the bar, inboard of the mounting brackets. Once you've got the bar centered and you've tightenend the mounting brackets, slide one collar over to the inside edge of each bracket and tighten them down. This will locate the bar laterally (you'll notice the OEM bar has rubber bushings that serve this function), and keep it from "walking" to one side or the other, which may in turn prevent you from breaking the OEM swaybar mounts.
Iain