FCS Fusion fin boxes were invented because of the growing popularity of EPS/Epoxy construction. Not to say you can't use the traditional X-2 plugs but it's a longer process. You need to pour a little epoxy in the hole to set the plugs, then a few hours later you finish off with more resin. A 2 part pour reduces exotherm which melts the EPS causing a weak install. It's a must to use Resin Research Quik Kick resin for plugs for less exotherm. You can also put cold icepacks under the fin area while installing to reduce exotherm. In our opinion FCS Fusions are better overall for ease of install and strength.