[Arran]

Did you try brake cleaner on the stain or carpet cleaner? Since it's a water stain I wonder if alcohol might remove it? I'm just wondering if that stain is dirt or a water stain? If it dirt the pint won't stick to it. Another thing you can try is GoJo, the cream stuff without the grit, but you would have to rinse it off afterward, but since the cloth is glued to the board if it were pinned down with staples and allowed to dry slowly it shouldn't shrink. I asked the dry cleaning place here about cleaning grill cloth but they throw everything into a machine so the cloth can't remain attached to a board, I don't know what they do elsewhere.
Regards
Arran