as I can’t answer on #jobicoz topic (no points) I have to do it like this.
Corecork as sandwich material is great for kiteboards, it is very strong and still provides enough flex.
I use a 100g/m2 45°/45° carbon under the cork in standing aerea and 2 layers of 4oz glas as outer glasing.
EPS is 30kg/m3 to get a rock solid construction.
more info you can also find here http://ahcustoms.ch/shape-construction/corecork-construction/
sorry for opening a new topic
