I think the main thing I need to fix here is the depth of the holes, and the fact that they taper slightly at the bottom, to accept inset screws.  I never even noticed that detail on the reference image, and I've never actually seen one of these up close, so I'm going to correct the holes to more closely match the real thing.  I just assumed they took an oversized hex bolt/screw.  But I just noticed that.  Also, the hole on the lip needs to be a little smaller.  I'll fix that before uploading the model.  I'll post screengrabs of those corrections to the flange soon.

Wish I had a real one to look at, because there's so many variations to these things, it's crazy.  ;)

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