Limiting the number of concurrent storage vMotions with vCenter 6.0

I have about 100 VMs to migrate to another datastore, but would like to minimise performance impact while doing so by limiting the number of concurrent Storage vMotions to only one, so that I can queue them all up and have them go one at a time.  (default limit is 8).

I found the below guides about how to achieve this, but was written and tested only with ESXi 4,  5 and 5.1 :

Limiting the number of Storage vMotions - frankdenneman.nl

Limiting the number of concurrent vMotions - frankdenneman.nl

vSphere 6 documentation seems to mirror what's Frank's last post:

vSphere 6.0 Documentation Center

So I tried adding in config key to my vCenter 6 and ESXi 6 environment like so:

  <vpxd>

    <ResourceManager>

      <maxCostPerEsx41Ds>20</maxCostPerEsx41Ds>

    </ResourceManager>

Then restarted vCenter virtual appliance, but was still able to Storage vMotion 3x VMs simultaneously to the same datastore...

I assume key has changed in version 6?  Any ideas?