i would recommend you start as simple as possible
multibody part with the foam modeled and then the skins modeled, use solid elements
then you can start going deeper with shells
and then you can add any spars...etc.
you also have to consider that this is going to be a good first step but the foam will have properties and the FRP will have properties that aren't necessarily linear or ansiotropic
Thank you for the help Jared!