Custom URL parameters (like .../(param1)/value1/...)
get lost on switching the pagelayout (e.g. ../layout/set/print/...)

I'm not sure how it was planned... possible fix in
kernel/layout/set.php:

$Result['rerun_uri'] = '/' . implode( '/', array_splice( $Params['Parameters'], 1 ) );
// added this to append UserParameters to rerun_uri
foreach( array_keys( $Params['UserParameters'] ) as $param )
{
$Result['rerun_uri'] .= '/(' . $param . ')/' . $Params['UserParameters'][$param];
}