Yeah, Newman was an unmitigated disaster.  Not only about this matter, but he was in fact a if not THE proto-Modernist with his notions regarding the development of doctrine.  While such COULD be understood in an orthodox sense (though the term should be avoided due to the fact that it's almost always understood in a heretical way), Newman clearly meant it in the heretical way.  Cardinal Manning (rightly) considered Newman to be a heretic, and several bishops from Great Britain denounced him to Rome as such.

Now, this is in fact one of the areas that proves that even a great St. like Pius X isn't infallible, since the latter defended Newman ... though undoubtedly based on a small sample size of his work that was presented to him selectively by someone favorable to Newman's position.

Newman basically told the Old Catholics who opposed VI that they should go underground until such as time as the dogma had "developed" long enough for them to come back out of the woodwork and re-interpret it (away).