I keep the break cue tip dead flat (zero dome) for two reasons:
-- Since the heavy power stroke while breaking can easily lead to the CB being struck off its vertical centerline, a totally flat break cue tip allows an error of approx. 3/16 either way, and the CB still receives a vertical center hit.
-- It seemed logical to me that more energy is transferred to the CB when there’s no dome geometry to compress upon impact, and my results verified that I experienced more ball scatter than I ever had with any kind of dome on the breaking tip. Try a dead-flat breaking tip configuration yourself and you may like this difference (if your results are similar).
Arnaldo