Builing new engine stringers in my Mariah 31 for a yanmar 3gm30f. I'd like to avoid using wood. I was doing the calculations on density, and noticed that the pink home depot insulation foam has a density 5.33. High Density Marine foam from generalplastics.com recommends between 6-20 pcf for stringers. Given I was planning to use plenty of glass; is this going to be close enough? Or should I just go with my original idea of building them out of G10 and not worying about anything.