Patrick. Did you try evaporust? If not, you could stack a couple paper towels over one of the stains, saturate them with evaporust, cover them with saran wrap & tape the perimeter of the wrap to seal it. Let it sit over night, and see what you get the next day. If you get any improvement, you could make a vat large enough to soak the entire top. A plywood frame with 6 mil plastic liner works great. Heed the temperature warnings on the evaporust. It matters! Use a space heater if necessary. Good luck with it.