Exactly what did you get? I'm thinking they may have given you a piece of minicell to cavre out a seat yourself. I would not expect they would have sent styrofoam as it absorbs water. Minicell is one of the most comfortable things for a seat you can get. I've seen many production boats that have had there production seat removed and replaced with minicell. Another place to look for seats is Newfound woodworks they have several options.

Kent