Assuming there really is an mdf box under there //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif and the sub is not mounted directly down to the metal but instead has a gasket material for isolating it and reducing vibration transferral to the metal... I like it. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
And yes, I see the carpet on the bottom side, so I know there's mdf under there. I say good job. I bet it will look great installed in its proper place.