If needed, you can also partition the customers table by the composite method. For example, you partition it by range on a postal code column to enable pruning based on postal codes. You then subpartition it by hash on cust_id using the same number of partitions (16) to enable a partition-wise join on the hash dimension.
You can get full partition-wise joins on all combinations of partition and subpartition partitions: partition - partition, partition - subpartition, subpartition - partition, and subpartition - subpartition.