The objective for my car is to build a tight, competant, solid, and sure-footed 400 WHP street car that composes itself efficiently on both smooth and cracked road surfaces, that is not only lightweight and strong, but relatively quiet with minimal NVH. The steering should be linear and communicative, with a low lock-to-lock ratio; a car exhibiting predictable and stable handling.

The thought of achieving as little flex to the suspension and steering components by way of Poly-Urethane Bushings and Heim-Jointed Links/Arms only to be compromised by a flexing chassis seems, in essence, no closer to meeting our objectives than that of a dog chasing it's tail or running 400+ WHP through the front wheels of a Honda Civic, or worse, a Hyundai Excel (JK, JK)

I have thought about foam for many years, having seen it for the first time, in, you guessed it, Sport Compact Car; back in the day of their Black and White Articling. The installation of the foam was performed on a Civic, if I'm not mistaken, but when the time came to actually implement this idea to my own project car, I had trouble sourcing it, let alone any valuable information pertaining to this process.... until now...

(Thanks FreshAlloy )

http://forums2.freshalloy.com/showthread.php?t=162693

According to Mike Kojima " Foamseal has foams in densities as high as 10 lbs per square foot if you desire to make things even stiffer. "

I asked the following questions on that thread...

So the question herein lies....what density is best to achieve optimal results?? (A simplified question deduced from a more intricate and multi-facted qualm, but nevertheless)

GUNLUV: In SAE paper 1999-01-1785 said "8pcf density gave the best strength to weight ratio." That would be best for rocker panels and frame rails.

But for pillars and joints, SAE paper #960435 said "the greatest benefit came from a ligther weight foam, as heavier foams didn't work that much better vs the cost and weight." also it mentioned, "there was no real benefit to be gained by filling the entire pillar" so PAY ATTENTION TO THE JOINTS.

so i would say 8lb density for rockers, and 2lb density of pillars and joints.
You have to pay attention to the flow rate, and expansion rate when you work with the pillars b/c spaces are limited. 2lb kit is ideal since you really don't want to add more weight with high center of gravity.

good luck with finding higher density kit with foamseal since that company does not exist anymore. So far all 6lb, 8lb, 16lb 2 part foam are not "injectable", most of them offer by other companies require pouring and mixing, so unless you can filp the entire chassis with a stand, otherwise some upside down location like pillars and lower frame rails are impossible to reach.