In reply to Beardyman:
I remember reading somehwere (maybe on the old beastmaker site) that all boards are sanded with a certain grade roughness of sandpaper so you could adjust the difficulty by sanding them.
To make the slopers easier to hold, sand them with a rougher grade
To make the slopers harder(!), sand them with a smoother grade.
Just don't do it too often or you'll wear your board out.