[rickst29]

Instead, look 1/3 to 1/2 the distance from the WDH ballmount to the stirrups. This is where the ends of the swing-hitch pins drop about an inch below bottom of the A-frame "arms". When the WDH stirrups are not hanging down loose, these hitch pins are the lowest point along each of the arms.

As your pictures show beautifully, the Trunnion-Bar is really tight to the A-frame arms close to the ball, and slowly increases distance below the A-frame "arms" as you move away from the ball mont - reaching maximum distance at the chains. But the Round-Bar is consistently far away, allowing for much more clearance and flex (without hitting the hitch pins) at the critical spot.

(IMO, the actually picture shows them a bit too far away: the chains shown on the very last link, and not "cinched up" shorter, as they would be in most properly-sized situations).