I put my amp on the rear deck upside down. I didn't put any spacers/brackets in there to lift if off though. I guess I didn't see it necessary as you wouldn't normally lift the amp off the bottom of ur trunk if you were to mount it on the floor. I put my cap on the backside of the box(box has little lip on the edge just big enough for the cap to mount to. Bought from Ebay). I didn't really have to put any holes in my car besides in the rear deck which will NEVER be noticed by anyone I might sell it too.
2008 G6 GXP Sedan
Dark Metallic Gray
Visual Mods: Rear 25% tint , 35% Front tint, 5% Eyebrow tint and sunroof tint. Badge overlays: Front, steering wheel, G6 door sill
Audio: Head Unit: Pioneer AVH-P4200DVD, (2)Rockford Fosgate P3D212 Punch 12" 500W Subwoofers, Rockford Fosgate T1000-1BDCP 1000W Amp
Misc: Escort Passport 9500ix
Future: HID Head Lights, Tinted Tails, Interior LED's