I assume you are talking about the Apollo 11 50th flat link.Yes, I have done this, and so have some other forum members.
I think the endlinks in this image are actually the A11 50th endlinks which I modified- but I originally had it on US hollow end links and it fit spectacularly. There was an incredibly slight difference in the sheen between the US endlinks and the bracelet itself which generally wasn't noticeable. It could be corrected easily by a watchmaker lightly repolishing both pieces together I'd think (unless the difference is a result of different steel types, which is also possible).
I didn't see any reason not to try to modify my original endlinks though, so I did that.