The old foam method was concrete blocks line with paper pour in the chemically activated measured and mixed foam solution clamp the two halves together allow the foam to blow , take out and mow by hand or machine CAD computer driven.
EPS foam shape to,a preset plug then vacuum bag is the way to go. You maybe could do it your way, but how will your design give the necessary strength and flex. Stringer? The shell you mold the foam in? EPS foam with soft plastic,,hard shell plastic?
Not saying no it could be a very interesting experiment.
Just do it where you are in a well,ventilated area. Many old foam blowers and shapers have had cancer from exposure!
