Seat mounting foam core deck

They go through the whole sandwich like a regular toggle but the toggle part is connected to a plastic retainer. You don't need to epoxy them unless you want to fill in the hole that is bigger than the bolt. You can also just shoot some 5200 in there and drop the retainer cap. Forget I said epoxy, just use a lot of 5200 under the seat flange so no rain water can get in and you are fine. If you ever want to remove the seat, the toggles will stay in place so you can put the bolts back in later.