Hello
The most common issue is that the transference of PIRs considers the first day of the period as the default date for transference. If you place the PIRs on another date, you may end up with duplicated quantities.
I have never tested this scenario by myself, so I don't know exactly which kind of other problems may happen, but I have already discussed it with the PP-MP-DEM architect and he do not recommend to place PIRs on another dates at all.
See this link for documentation about this scenario:
Demand Management: FAQ and consulting notes
BR
Caetano