Jeremy, I always have to do some resizing on photos - like everyone else - before I can answer your questions.
You pretty much nailed it all around.
The forward tang width is full width 1/2 through the spacer.
It takes about an hour, but a bit of filing on the frame face/lugs, the spacer slot and the tang itself, and I slowly creep the frame into place. I want everything to lock together with no slop.
The guard is driven on tight, so there's no up and down play.
The spacer and guard are pinned.
The frame then filed to fit the spacer.
The frame then bolted to the tang.
It's a tank.
Also notice that the frame is .008" thicker than the slot in the spacer.
You can see a little ledge around the filed lugs that will sit and push against the spacer, as well as the top portion against the back of the spacer above and below the hole.
Lots of pressure contact area.
Also, when I crank down on the bolt, this picture frame contact area on the back of the spacer won't let the frame move in any direction.
This is at a point where I'm just sneaking up on it.