If the correct location is in the Late Cenozoic, then the paleontological evidence would suggest a slower and less dramatic post-Flood diversification.
Sixth, since the boundary placement is foundational to developing Flood models, effort may be wasted if the location is not known.
Three positions were argued in Reed and Oard: The third position is mine, and I believe it to be a middle ground between the two, based on field evidence I have studied.
For more information, I recommend reading the cited literature.
However, all of them pointed to a Late Cenozoic boundary.
Most areas that I have examined from either field or literature research indicate a very Late Cenozoic boundary, often in the Early to Mid Pleistocene in areas not affected by glaciation.