allz i know is it doesnt increase the spl but the sq is better. you can do it for both types of boxes but u have so put a like mesh grill or something like that over the port to stop the stuffing to be blown out.
Stuffing or lining a box with poly fil makes the box appear larger to the woofer. A stuffed sealed box will play lower then the same box not stuffed because stuffed appears larger to the sub. Can be used in most box designs.