Hello,
styro core foils for a cat are a pipedream in my opinion.
Most foils on production cats(NACRA's and Hobies) are foam core. Marstrom carbon foils are foam core (Tornado's are hollow core), Mine are are foam core.
The techniques used to determine the shape and size of the core is very similiar to the techniques used to calculate ribs for aircraft wings, it dates to 1910-1920
You do have to taper the trailing edge
