ye its essentially same thing, it just hardens with the resin apparently like fibreglass and leaves a good finish surface for painting/vinyl providing that layers of matt are applied from the inside of the box. i never used it my self, but i read a few things bout it and it in a few car show once in which they used the fleece and only one layer of glass to make a roof lining of a car for tv screens, i think it was pimp my ride
ye adding a port would make it louder and drony
i dont like my box cus of the MASSIVE port AND cus its very huge and annoying
edit
i just googled fleece + fibreglassing AGAIN and its prefered because it soaks resin good and dosnt crinkle much
hope that helps man