anything solid will create more squeaks. egg crate uses the foam to deaden and the egg crate shape to deflect echos. raammat
and ensolite foam
is what i researched and used. since you already have dynamat, just use the ensolite over it. both were very well rated on the sound deadening runoff. i used both on the firewall, back wall, doors and under carpet. my truk is still noisy from leaks around doors.