what can i say, confidence is a good thing. but greatness is in accepting and learning from mistakes 
as for the 3002d4 sub, I believe every sub has a different behaviour if placed in the same enclosure. "relatively" peaky 50hz subs generally need large volume ported enclosures, which is why they sound flatter and better in a sealed setup.
factory suggested enclosure sizes speak volumes about a sub's actual requirements.... 