<?php
//Try in functions.php
function bow_welcomepack_s2member_redirect( $url ) {
  if ( !$WPUser = get_currentuserinfo() )
    return $url;

  return dpw_first_login_redirect( $url, '', $WPUser );
}
add_filter( 'ws_plugin__s2member_fill_login_redirect_rc_vars', 'bow_welcomepack_s2member_redirect', 10, 1 );
?>