extend Leads default filter

On the Leads List View I would like to override the default filter to search account_name rather than first_name & last_name.

I've tried adding the following lines in both the ./custom/modules/Leads/clients/base/filters/default/default.php & ./custom/Extensions/modules/Leads/Ext/clients/base/filters/default/default.php files

$viewdefs['Leads']['base']['filter']['default']['quicksearch_field'] = array('account_name');
$viewdefs['Leads']['base']['filter']['default']['quicksearch_priority'] = 1;

This is not working.  This exact method of overriding the default search works on Cases where I first tested it.  I tried modifying the ./modules/Leads/clients/base/filters/default/default.php file directly with the above change and that did work, so it's just not letting me extend Leads with this functionality.

Any thoughts on this would be appreciated.