Seats.

Finally settled on a seat design.

34mm square pine stock. Edges rounded over on the router table, and then a vee-groove routed into the pine.

6mm marine ply for the spreaders, with no stiffening since the rails will be screwed to the boat.

The the ply was chamfered with a plane, and then filleted to the rails with thickened epoxy.

Closed-cell foam will finish the surface off, and provide padding for my bum, once the seat's been varnished.