The MP ones were junk.
I had one wear out on the dyno.

The problem is, they often rough up the eccentric on the cam when they fail...... Then you're kinda screwed.

If the Mancini ones are truly .001-.002 oversized....that would fall into my "that's just dumb" file.
If they thought there was a need for an oversized one...... It should be an "option", not the only way it comes.
And there should be some paperwork, or notice on the packaging stating its oversized.

As stated, the best bet is often to find a nice used factory one.