Machining rocker in light foam

Good day all

I’m running a CNC machine cutting surfboards but I’m having a problem when cutting light EPS foam. Once I’ve cut the deck and flip the board over, I need to set the brackets to hold the board to maintain the correct rocker. The problem is that the foam is so light that it will fold to wherever the brackets are at. With a normal board with a stringer, there is enough strength for it to hold it’s rocker.

Does anyone have any ideas for me?

https://www.instagram.com/p/Bc40BSJgHFh/

AMAZING!!!