Bill Shaw indicated that the variations in displacement may result from the industry's shift to 50% from no load - ie., 1/2 fuel, 1/2 crew, etc.

Origianally the Ariel was shown at 5120 and the Commander 5100. Later (after the 1/2) the Ariel was shown at 5500. (There is a missprint in the manual showing 5320 for the Ariel.)