Solved!
public function __construct()
{
parent::__construct();
$part1 = array_slice($x->fields_list, 0, 1);
$part2 = array_slice($x->fields_list, 2,1);
$part3 = array_slice($x->fields_list, 4, 4);
$part4 = array_slice($x->fields_list, 8);
$this->fields_list = array_merge($part1, $part2, $part3, $extraFields1, $part4);
AdminController::__construct();
}