Ive used two types of Dow XPS in the past…white and blue…as far as I was told by Dow , the only difference is the colour. There is another one = Dow pink . I was told that the “pink” had memory…ie it would robound from a heel dent without creating a small delam. I built an 8’ 6" log using both white Dow and blue dow. The board was primed with straight epoxy , no thickener to keep the viscosity low , and penetrate the foam as much as possible.It did penetrate…not as much as EPS does , but it did penetrate enough to put a hard skin on the foam’s surface , therefore increasing impact strength…and creating a more than adequate bond between the glass job ( 2 layer of 4oz) and the primed xps… The application of the prime coat was by squeegee , using enough downward pressure to force as much as possible into the foam surface , then removing all possible resin off the surface with squeegee , then wiping with tight celled sponge brush. Although the board has not had a lot of use , I did ride it regularly for about a month…and my bro used it regularly for almost a year… its now a spare board , and someone grabs it for a wave every now and then…it has no heel dents so far, or signs of any delamination…I built this board about 8 years ago.