has an one used closed cell polyurethane expanding foam on their crx's in the nooks between the body and frame e.g. in the hatch area to stiffen te car and stop squeaks. supposedly a 2-4 lb density will do wonders...

 

Never heard of this; hope someone can shed some light

 

I just use a rear floor bar along with the strut tower bars and I have no squeeks, rattles or shakes in my civic

 

put in a roll bar. it will make for interesting driveway teetering antics

 

you are talking about high density foam that you mix and pour into cavities of the car, increasing the structure and quieting the panels. very worth while but somewhat expensive and messy. it is a must do on my list of things.

Here is some info
https://honda-tech.com/zerothread?id=616530
stan

P.S. read your post over... definately consider higher density readings than 4.
about 40-60 is more like it.

 

Rear reinforment bars definately tie up the chasis better and prevent such squeeks.

 

my "reinforcement" bars in the back provide a horizontal surface to put my drying laundry. they do not do anything for handling or structural integrity of the car. foaming is an old trick, used my BMW owners and "boxes" in the otherwise moving tack-welded panels.
stan