The tangs are welded onto the end of the boom, and there is a stiffener brace welded on either side (barely visible below the nut in the picture). The tang starts to bend forward of the stiffener brace on the side.

I'll ask Mark, the owner of the boatyard for his opinion. My hunch is I could bend it back into place because the bent part it is not directly in a welded area. I was going to use a bolt with nuts and fender washers on the inside of the tang, and gradually force it apart - while preventing the aft part of the tangs from being bent out with a C Clamp. The net effect being only the forward bent part of the tang should move. It only needs to go enough for 1 or 2 washers on either side.

The tang itself is rounded on the end and a 2" fender washer covers the entire area, so that should act as a sufficient coverage. If not I'll make some plates as Brian suggests.
Rob, you're correct it doesn't twist all that much, so perhaps I'm over-worrying. However, it does seem like even a little twist would put a stress on the upper tangs of the rigid vang in a direction that could snap or bend them.

I'll let you know what I decide to do and how it turns out. Thanks again for the thoughts so far.

Max