I did 1/2" coosa on my deck, at the span over the fuel tank(~24") I cut up scraps and added strips of the 1/2" coosa to give it extra rigidity. It's rock solid everywhere. Rather than paying the extra for 3/4".

1/2" on my 18. Solid as a rock.

What was your layup topside and bottom, and how much epoxy did you use? Trying to get my order together.