There are 25,000 seats on the sidelines at BMO. To reach 40,000, a temporary 15,000-seat grandstand would have to be erected in one end-zone...which would be bigger than either sideline grandstand. A technical impossibility, I believe. More likely the maximum capacity will be in the 36-37,000 range. I think that's perfectly fine for the Grey Cup these days, it should be tremendous event!