VPLEX in 3rd party rack - do we need 1U spaces between components?

Seeking some guidance...

We are installing a VPLEX Dual engine solution into a 3rd party rack and the EMC site prep guide has 1U spacing between every component. Is this spacing required - 22U space for 13U of VPLEX components.

As this is a managed data centre that the VPLEX is being insatlled in, every rack unit costs money.

If the 1U spacing is required for airflow, the data center provider does not allow "open" rack units and they will have a blanking plate put in place, which will stop most of the airflow.

Can we install the VPLEX Dual engine solution using only the 13U, not the 22U that includes the blank spaces between components?

Cheers.