Sorry I didn’t catch some of this, I’ve been out backpacking for a couple nights.
I would be very surprised if anything other than fiberglass was used for those decks, and the same gel coat as the hull for appropriate color matching. The “premium” designs by Phil like the Ariel and Zephyr would have the decks above the tanks, mostly for aesthetics would be my guess, the Shadows are using a float tank design that comes up high enough to be a “deck” as well (TomL’s Combi really shows off Phil’s tooling ability in the tanks).
The boats with a pedestal didn’t require tanks as the pedestal should provide the positive buoyancy needed when swamped, but now I can’t remember what was done on the Fishhawk version with a bench. Maybe they just expected the owner to add air bags/foam like other companies have done with some boats (Esquif Mistral)?
Also, per your earlier thoughts on swapping out the pedestal for a bench, I know a few boats that were designed for the pedestal won’t structurally take a bench as the sides weren’t built up for it. I’m not sure about this model since it was shared with a benched version, probably only something Phil or Bob Brown would know, sadly Phil isn’t around anymore to correct all of us. Dave Curtis (Hemlock Canoes) may remember, he was close with Phil and they sold each other’s boats for a while.