It solves the problem of Father Cekada's "Aunt Helen" being able to wake up one morning and simply decide that a Pope is illegitimate and not the pope.

In straight SVism there's no room whatsoever for the authority of the Church, which absolutely must play some kind of a role in determining whether a Pope is truly a non-pope.

It addresses the same problem that John of St. Thomas articulates with regard to straight SVism, where the Church would be in chaos if any private individual could simply determine that a Pope is illegitimate at any given time.

Thank you for this explanation. Will you please expand on what you mean by room for the Church's authority? Specifically, are you saying that there is an instance in which a sedevacantist would disregard the Church's authority (and the sedeprivationist would not)?

It attempts to solve the Crisis problem

No, it attempts to EXPLAIN the problem in theological/doctrinal terms.  

And I might be missing something here, but I thought all Papal writings are contained on the Vatican Website?  For some reason my searches for this docuмent on the Vatican website are coming up with nil.

No take on the Crisis solves -- or is meant to solve -- anything.  Each and every one is an attempt to ascertain what happened during and after V2 and what that means with respect to the identity and whereabouts of Holy Church.  

Even if God helped one to understand every single aspect of what happened from that day to this, NOTHING would actually be SOLVED.  

Straight SVism is untenable due to the argumentum ad absurdum of allowing Father Cekada's "Aunt Helen" to wake up one morning during the reign of Pope Pius XII (or a future Pope Pius XIII) and decided that the See is vacant because she had discovered heresy in his teaching.

This is a problem that has never been adequately addressed by the straight SVs, and something that Bishop Sanborn also came to understand.  There has to be some principle to prevent this type of "chaos" in the Church (as John of St. Thomas characterized it), and that principle is not clearly articulated by SVs.  See, one could argue from Universal Peaceful Acceptance, but then UAP seems to fly in the fact of SVism, since Roncalli and Montini (at least in the beginning) were certainly universally accepted.

The argument to this is that Aunt Helen could just be plain wrong and context matters.  If I wanted to go through let's say...Pope St. Linus's teaching and take something out of context and find "heresy" then the right way to handle that is to say they are wrong on the matter and to recant and in charity show them or tell them why they are wrong. 

That's beside the point.  Of course one should try to persuade Aunt Helen that she's wrong.  But that would be your opinion against that of the Linus-vacantist.  There has to be an objective standard to know who is a Pope and who isn't, not just your private opinion that this individual is wrong.  And it isn't just about whether the individual is wrong materially in their interpretation of Linus' teaching, but that they are wrong to be holding that popes are not popes in principle.

Let's say that someone decides that Pius XII was also non-pope because, according to him, Pius XII was a heretic for condoning NFP or condoning evolution or for permitting the liturgical changes, etc. ... and there are some out there who hold this.  What principle is there to prevent the individual from coming to this conclusion.  At this point, then, for this individual, the dogma of the Assumption is no longer a defined dogma.  Similar with Pius IX, and the chap I knew who decided that he was a non-pope.  At that point, the dogma of the Immaculate Conception is no longer a dogma, nor is the dogma of papal infallibility.  If Aunt Helen can start removing popes, then Aunt Helen can also start removing dogmas.

Now, some hold that Universal Peaceful Acceptance provides the necessary a priori certainty regarding the legitimacy of a pope, and that the pope's legitimacy is known with dogmatic certainty.  Some theologians, however, only hold that the pope's legitimacy can be known with moral certainty, and they make a lot of good points.  Then you have to determine what constitutes Universal Peaceful Acceptance.  This is a complex issue.  But Universal Peaceful Acceptance poses a problem for Sedevacantism, since by the most accepted definition of the term, Roncalli and Montini (at least initially) had such Universal Peaceful Acceptance.

Related question, if we know, how do we know which popes were the true popes during the Great Western Schism?

Also, if Urban VI was the true pope, peacefully accepted, but subsequently rejected by 15 cardinals, what does that make those cardinals if the person of the pope is a dogmatic fact?

Certainly they can't be called neither schismatics nor heretics for doubting the validity of the election.

In practical terms, does being a sedeprivationist vs. a totalist/sedevacantist differ in terms of actions taken? Or would it only, theoretically, be in future actions, e.g. accepting a Novus Ordo pope who converted?