I'm looking for information on Detroit & Mackinaw RR's rock trains. As I understand they were loaded in Alpena and a major customer was Dundee Cement on the AA. Were there any other customers? Because of the weight were the hoppers only 1/2 full? Is the quarry still open in Alpena? Any other interesting info would be appreciated. I have some of the DM HO scale hoppers and I'm thinking of modeling parts of this.