I do want to point out that while hybrid slots will take PXI modules, the modules themselves need to be configure correctly. Normal PXI modules had a full backside connector. These need to be modified to be able to be inserted into a hybrid slot. The modification involves removing a portion of the connector to fit around the PXIe portion of the backplane connection.
Take a look at Figure 4 from the following link:
http://www.ni.com/white-paper/3882/en/
If you have existing PXI modules with full backplane connectors, you should be able to call NI and have the modules sent in to be modified to fit in hybrid slots.