Exchange SP3 Schema Updates

I understand that the updates in Exchange 2010 SP3 are cumulative. However, are the schema updates cumulative?We're running Exchange 2010 SP1. We have have Blackberry in our environment. We understand that SP3 has not been vetted just yet. However, RIM doesn't seem to have any problem with SP2 RU6.We're wondering if its possible to update the schema with SP3 but then install SP2 RU6 until RIM has confirmed that there are no issues with SP3