Ultimately, the problem with the new-sspx is that it did not update its philosophy on new-rome once all the old, valid, novus ordo priests died. Now that new-rome is 99% filled with new-rite bishops/priests, the "positive doubt" about such is VERY GREAT. I don't see how anyone could argue otherwise.
PlenusV, you're making an argument based on decades-old data. This is why it's faulty.
No, I'm arguing a principle, which does not change with data.
But I agree with you entirely, that over time, the doubts as to validity increase, as clearly expressed in Archbishop Lefebvre's letter to Mr Wilson. Eventually there will be no priests left in the Conciliar Church who were not ordained by newrite doubtful bishops. The presumption must be against validity now more than ever.