WTF?...300% stiffer....from foam? If you believe that, then I have a pretty red bridge to sell you. It used to be known as the "Golden Gate Bridge" but it is now known as Randy's Bridge. For the small price of say......a turbo kit, it can be yours!!
But seriously. I guess anything is possible, and filling in holes with weaker material has a much larger effect than one would think. BUt 300%??? That is a little too much for me to believe.
The Proud owner of a big red bridge