Man I hear you, Mine does the same thing, guessing not as bad though. At my stereo competion my girlfriend was playing a Bass Mechanic CD and listening to sweeps and I was standing outside, roof was open, and the roof of car is bouncing like 2in. I was amazed that my sunroof didn't crack. she played someother tones and couldn't find waht frequency, went through whole test cd, went back to the sweep tracks and theres my roof juping around. I don't really want to take my headliner down and dynamat. lot of work. I do hear that SQ speaking I hear that you will notice a big time silence when the roof gets done. If it'* bad, you have no choice to dynamate everything, not talking one layer, take apart the rear deck and put 2-3 layers there and work your way up, I say if you got it all apart, might as well put 2 layers and 3 were you need the most reinforcement.
Caution-One bad thing I did was put 2 layers on the top part of the rear deck and it rose the whole carpeted trim plate and made it touch the glass in the back, alloying for a nice rattle suprise after all my dynamating. First I put two grey screws in it to hold the read deck together tight and put a thin piece of foam rubber as a spacer along the rear glass and all the way around the rear deck trim piece, to stop any chance of audiable vibrations. Good luck. Spent many hours seating in back seat pushing on things to "find the rattle" still have a couple to go.
2001 SSEi 13.731 @ 101.59--->PICS HERE <---
--Intense PCM--2nd gen LSD--3rd gen Rockers 1.9 --#105lb springs--oil restriced pusrods--Intense shift kit--TEP CAI--ZZP mod 3.4/3.2 --IAT relocate--TOG silver ceramics--SLP CAT--o2 fake--160 stat--PRJ 10.4mm wires--Autolite 104'* @ .055--MAP TB heat shield
--Custom mesh grill--Cleared front and rear corners--Angle Eye'*--Silverstars 9006+9005+H3--PONTIAC 3rd break light overlay--Embrodered PONTIAC head rest wrap--Arrowhead inlays for front+rims+steering wheel--Zaino polish
--Alpine IVA-D300 7in TV--two 10W7s--JL amps 1000.1 & 450.4--MB Q'* 6.5in Comps--Optima yellow top--5 farad cap--lots of dynamat extreme--Custom install w/ plexi and mirrors--Sirius radio--compete in Sound Quality!!!
------PROTECTED BY VIPER!!!!!!!!!!------