Dear Stubborn, I respect those holy Priests (and holy Laity!) that made great sacrifices to keep the Faith, hold to Tradition and pass it down. There were of course such good Priests outside the SSPX, Fr. Wathen is one; Fr. Gommar is another http://www.latinmass-ctm.org/pub/archive.htm Granted the terrible confusion of the time in the late 60s and early 70s, it was not necessary to pass any judgment on validity. All that was necessary was to use the traditional rites and hand them down. The SSPX finally undertook what is probably the best and most exhaustive study of the question till date almost 40 years after they were introduced, namely in 2005. Resolving the question of the validity of Priestly Ordination proved to be rather simple, because only one word is changed in the essential form (What theologians call "essential form" is analogous to the Words of Consecration in Holy Mass, or the "I baptize you ..." it is not meant to be used alone, but even if used alone, it will validly confect the Sacrament, though with a loss of grace). The question of Episcopal Consecration was far more difficult to decide, as Fr. Pierre Marie recounts. What greatly helped in the final resolution of the issue was finding the third century work of St. Hippolytus called Apostolic Tradition in use in at least two Eastern rites. What Rome tried to do was mix and match western and eastern rites, with an unhealthy dose of errors and excuses like antiquarianism and ecuмenism thrown in. It was unnecessary and we can and will use the traditional Roman rites. But the new rite is basically a form found in Eastern rites. There were those who suggested the same earlier to Archbishop Lefebvre, as Fr. Cekada (in a biased manner) recounts, "By 1982, however, once [Archbishop] Lefebvre undertaken another of his periodic bouts of negotiation with the Vatican, he changed his position, apparently under the impression that Paul VI form was used in the Eastern Rites, and therefore unquestionably valid." It remains to show that the "impression" is correct.

Priestly Ordination:

Old Essential Form: “Da, quaesumus, omnipotens Pater, in hunc famulum tuum Presbyterii dignitatem; innova in visceribus eius spiritum sanctitatis, ut acceptum a Te, Deus, secundi meriti munus obtineat censuramque morum exemplo suae conversationis insinuet.”

New Essential Form:“Da, quaesumus, omnipotens Pater, in hunc famulum tuum Presbyterii dignitatem; innova in visceribus eius spiritum sanctitatis. Acceptum a Te, Deus, secundi meriti munus obtineat censuramque morum exemplo suae conversationis insinuet.”

The only difference is the single word "ut" that means "that". The translation is, briefly, “Grant, we beseech Thee, Almighty Father, invest this Thy servant with the dignity of the Priesthood; do Thou renew in his heart the spirit of holiness, so that [the new one would be almost same, except there may be a fullstop here] he may persevere in this office, which is next to ours [means next to the Episcopacy] in dignity, since he has received it from Thee, O God. May the example of his life lead others to moral uprightness.”

Episcopal Consecration:

Episcopal Consecration is more complicated because the rite is completely changed; it is not the traditional Roman rite at all that we're used to, but an old rite that appears to be in use in the West Syrian and Coptic (both Catholic and Orthodox) rites. It is not as expressive as the Old Essential Form, which was, “Comple in Sacerdote tuo ministerii tui summam, et ornamentis totius glorificationis instructum coelestis unguenti rore santifica.”

I.e. “Perfect in Thy Priest the fullness of thy ministry and, clothing him in all the ornaments of spiritual glorification, sanctify him with the Heavenly anointing.” - the preceding sentence is "And therefore we beseech Thee, O Lord, give bountifully this grace to this Thy servant, whom Thou hast chosen to the ministry of the Supreme Priesthood, so that what things soever those vestments signify by the refulgence of gold, the splendor of Jєωels, and the variety of diversified works, these may shine forth in his character and his actions." followed by the essential form above."

The new form is different: "Pour forth now that power, which is thine, of Thy Principal Spirit, which Thou gavest to thy beloved Son Jesus Christ, which He bestowed on His holy Apostles, who established the church in every place, the Church which thou hast sanctified unto unceasing glory and praise of thy name. Thou who knowest the hearts of all, grant to this thy servant, whom thou hast chosen to be bishop, [to feed thy holy flock] and to serve as thy high priest without blame, ministering night and day, to propitiate thy countenance without ceasing and to offer thee the gifts of thy holy church. And by the Spirit of high-priesthood to have authority to remit sins according to thy commandment, to assign the lots according to thy precept, to loose every bond according to the authority which thou gavest to thy apostles, and to please thee in meekness and purity of heart, offering to thee an odour of sweet savour." The first sentence is designated as the essential form. It is not the same form, but it is a quasi-Eastern form - it was chosen because of its ecuмenical appeal - but its use in Eastern rites assures of its validity. Moreover, there are clear references to the Episcopate, just as in the traditional form. "fullness of Thy ministry", "Spirit of High Priesthood", in the old rite, "Supreme Priesthood [i.e. Episcopacy]", in the new form, "which He bestowed on His Holy Apostles [who were made Bishops] etc.

Here's Fr. Pierre Marie's original study for those who wish to pursue their inquiry further: http://sspx.org/en/validity-new-rite-episcopal-consecrations. "Let us note in passing that these two rites are perfectly Catholic ... To assure ourselves of the validity of Pope Paul VI’s rite, it will suffice for us to place side by side the new consecratory prayer and the two Eastern rites in question. The validity of these two rites can in no wise be called into question, otherwise the Coptic Church (Catholic as well as Orthodox) and the Syrian Church (which includes the Maronites) would have neither bishops nor priests, nor would they ever have had them. We have prepared a four-column comparison (refer Table 3: Four-column comparison of 1968 edition with Hippolytus text, Coptic and Maronite Rites) with, in order from left to right, Pope Paul VI’s new consecratory prayer,[77] the Latin version of the Apostolic Tradition [i.e., “of Hippolytus”—Ed.],[78] the Coptic rite, and the Syrian rite. For the latter two texts we have used the Denzinger translation.[79] With the four prayers transcribed into the same language, the comparison is made easy." See Table 3 http://sspx.org/en/table-3-validity-new-episcopal-consecrations

Resolving the question of the validity of Priestly Ordination proved to be rather simple ... The question of Episcopal Consecration was far more difficult to decide, as Fr. Pierre Marie recounts.

Only the Church is competent to "resolve" and "decide" this question.  Yet, according to you, since you have no doubt regarding the legitimacy of the NO hierarchy, the Church has in fact resolved the issue and decided ... in favor of their validity.  So there's no need for you to cite any other sources from Traditional Catholicism.

And even those who harbor positive doubts regarding their validity have not resolved or decided anything.  There's merely enough evidence there to constitute positive doubt ... and therefore the obligation to avoid.  Implicit in this issue is an implicit doubt regarding the legitimacy of the NO hierarchy, since it is not possible that the Church could promulgate a doubtful Sacramental rite.  So sedevacantism and the question of NO validity go hand in hand.