Foamseal's two-component foam kit, p/n 11-22 is what modified mag used in their article on stiffening the z32 chassis. If I'm not mistaken this product is 1.75lbs. Per cubic foot. I will be doing this process soon and from the meaduring I've done you'll need close to 20 cubic feet. That's 35lbs. Or so added to the chassis. My only concern with this would be the foam detoriating and allowg moisture to build up.