I'd just conditionally baptize every single convert (including from the Novus Ordo). You should supply the missing rites anyway, and at that point you might as well conditionally baptize. I really don't understand the extreme reluctance towards CONDITIONAL Baptism. There's absolutely no harm done, since IF THE PRIOR BAPTISM WAS VALID, then there's no confection of the Sacrament. There's absolutely no risk of the "sacrilege" of repeating the Sacrament. That's the whole point of a conditional. Now, if you're being frivolous, such as a scrupulous person who might seek to get conditionally baptized on a daily basis, that would do harm to the Sacrament, but to do so one time for a convert, it's absurd that there's even a question. What if your "investigation" yields an incorrect finding and the person loses his soul because of your "investigation"? Some of this has to come from a lack of sincere belief in the necessity of Baptism and the Sacraments for salvation.