DynaMat

me too

66hertz, I used that stuff too. Went on fine, you have infinite control over where to put it and how much since it's a viscous liquid. Took a good while to do all the coats - I have a whole 5 gal. bucket on floor pans, rear divider, inside quarter panels, up to the firewall. There are still squeaks and rattles from above since it's a convertible, but not much sound from below. I think it ends up being lighter and less bukly per-unit-of-sound-absorption than the mats.

 
hopefully you restored it 1st

floor pan was replaced prior to this, SEM was applied in hard to reach places, and this over it. It's probably going to be pretty hard to remove short of having it dipped, but I never plan on doing the pans again, the car never sees rain.

I would only apply to pans, etc., AFTER rust repair - I couldn't do my trunk for this reason.
 
go with dynamat. it costs a little more for a reason. all those knock off products dont even come close, trust me, i've tried them. i dynamatted my entire interior, there is ZERO road noise.