Eibach makes pretty good S___t! You should be willing to trust their stuff. AWE has an H&R 28mm "Time Attack" racing rear arb that you may be interested in, although any adjustable arb is sufficient for most driving styles. Sorry for side tracking the topic, just stating my obvious sadness that I got the 26mm H&R right before they advertised that they had the 28mm arb.
Anyhow, Eibach will surely stand behind their product should you be dissatisfied with performance or fitment. But, might be something to ask about.