Hanno,
I haven't measured the two types of Canadian 16" rims to confirm actual size and shape but what you are saying ("The six-stud CMP wheel was used on 8-cwt trucks. It doesn’t have a different bead taper, it simply has a smaller diameter") is in conflict with the AEDB design record that states the rim for use with 9.25-16 tires has a 5 degree rim base taper and the rim for use with 9.00-16 and 10.50-16 tires has a 1-1/2 degree taper. The AEDB record doesn't give a diameter at the bead seat other than the nominal 16".
Mike's measurements (taken from tires) show both a smaller diameter and a greater taper (assuming the tire wall was of similar thickness at the bead seat) for tires intended for use with the "American" rim.
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