How to set a dynamic default value for a report plugin parameter of date type in Jira 7.5

I had solved this problem by creating a webwork action for the ConfigurerReport class. I set the property like this:

 <property>
    <key>startDate</key>
    <name>report.requirements-growth.issuecreation.startdate</name>
    <description>report.requirements-growth.issuecreation.startdate.description</description>
    <type>date</type>
    <values class="com.atlassian.plugins.tutorial.jira.reportsutils.ProjDefDateGen"/>
  </property>

The the class ProjDefDateGen returned with the desired calculated date value

Which I recover in the overridden function: public String getParamValue(final String key) of ConfigureReport class.

But I just migrated to Jira 7.5 and I see that ConfigureReport is no longer in the actions.xml file, therefore cannot create a webwork action to override it, also one of the parameters of the constructor is private.

So, how can I now set a dynamic default value for a report plugin parameter of date type in Jira 7.5?. I don’t know if the Object-Configurable parameters for reports changed. I don’t see new documentation about it.

Regards,

Edgar