Originally, Ensigns did not have a boom vang. Original Ensigns had roller reefing and no vang as the vang would make roller reefing nearly impossible.
I changed from the wire into a slot under the boom to a bail on the boom a few years ago. The wire had a tendency to break when least expected, and most needed. No bail on the mast. My boat has a fitting purchased from Ensign Spars (under Zeke) many years ago. The fitting fits into the slot on the mast near where the mast goes through the deck - keeping the entire vang on centerline.
Nick Lubar
Fleet 29