Pilgrim, the advantage of divinycell over your blue foam will be in the shear strength. This is the crucial property when designing a foam sandwich structure. The flexibility is actually an advantagous feature not only in building but also in the strength of the final structure is it means the skins will take the majority of the load instead of the foam. Most people would use primarily 80kg foam for your application. The 60kg will bruise easily unless you put a lot of glass/carbon over it.