Then I sanded things smooth, coated with epoxy + filler (this 4mm ply has a pretty crap open-grained face ply, which swallows epoxy), then a couple of coats of unthickened epoxy, then sand down to 180 grit, and finally toplac paint.
Here's what it looks like tonight.
Next job is to complete sanding the decks out to 180 grit and then paint them with top coat. No, I'm not using undercoat. I really dislike the stuff - it clogs emery way too fast for my liking.