My new spider gasket has two different shaped side: a smooth side and a 'ridged' side. The pool store said to put the ridged side down into the grooves with the smooth side up. Videos I've seen have it the opposite, with the smooth side down into the grooved with the ridged side up. Need some advice on which side goes up. The multiport is a PAC-FAB SM-10-2 DE, 2". Thanks.