i have wired up my new sub and amp to a tutorial on here and dont know where to ground the amp. on here it says in the side pnel that clips off there are 2 white bolts and to connect it to on of these, i have done that and get no power at the amp. it looks like around the bolt it has like foam and this obviously would make it not work. where can i ground the amp to? i dont really want to drill any holes.