Leads conversion mapping custom relationship

How can I map in the leades conversion a specific leads-field to a custom_relationship? In my case a one-to-many relation from
contact -> oppportunities!.

Here is my adaption in the convertdefs.php, which works fine manually, but does not map automatically?:

$viewdefs[‘Opportunities’][‘ConvertLead’] = array(
‘copyData’ => true,
‘required’ => true,
‘templateMeta’ => array(
‘form’=>array(
‘hidden’=>array(
‘’,
‘’,
‘’,
‘’,
‘’
)
),
‘maxColumns’ => ‘2’,
‘widths’ => array(
array(‘label’ => ‘10’, ‘field’ => ‘30’),
array(‘label’ => ‘10’, ‘field’ => ‘30’),
array(‘label’ => ‘10’, ‘field’ => ‘30’),
),
),
‘panels’ =>array (
‘LNK_NEW_OPPORTUNITY’ => array (
array (
array(‘name’=> ‘name’, ‘displayParams’=>array(‘size’=>90)),
),
array (
‘amount’, ‘account_name’,
),
array (
[color=#bb0000] ‘contacts_opportunities_1_name’,[/color] ‘project_opportunities_1_name’,
),
array (
array(‘name’ => ‘description’, ‘displayParams’ => array(‘rows’=>10, ‘cols’=>90) ),
),
)
),
);