1- am not sure how big the whole should be for a 15 (definitly NOT 15).
2- leave the rubber around the sub, its there to be kind of air tight, when mountenin the sub.
3- liquid nails - yes , and many other ,example silicone.
4-a terminal is always the best idea, if not, just make the wires comes out from the port //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif.
5- wtf, how come the cone is covering the holes ?? u mean the rubber at the sides of the woofer, is covering the, nail holes in the woofer ??
6- no it doesnt have to be centered, but if it was for me , i would have mounted it in the center especially in ur design, it looks more sexy in the center. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif
and hey after you are done send us some sub ****.
and am from sudan-africa. but am half casted, turkey-paki-sudanese PEACE