We're talking about the almost ready to fly version? I've seen it but not assembled one. Normally, the firewall has a round cutout that the cap of the fuel tank fits into. Try and see if your tank fits snuggly. Also, they may give you enough room to pad with foam, but you may not have it either. I've seen some that leave no room for foam. It isn't critical. If your tank fits snuggly, get it glued whatever way they provide and don't worry about the foam part.