In this section of his multi-part teshuva on yichud issues, Rav Waldenberg discusses the problem of yichud of one woman with two men. According to the Gemara in Kiddushin which serves as the basis for this entire discussion, one woman is allowed to be secluded with two men, althogh the Gemara then qualifies this by stating that this applies only if the individuals are צנועים, modest people. However, if they are considered to be פרוצים, lax in the sexual morals and behavior, then even a larger group would be problematic.
Rav Waldenberg's teshuva revolves around the basic point of who is considered to be a פרוץ and who is considered to be a צנוע. The initial problem stems from a statement of Rav in the Gemara who formulates a ridiculously high standard of who is considered to be a צנוע (using another אמוראas an example - the stories of that אמורא are found earlier in Masechet Kiddushin). Rambam basically codifies this view and rules that by his time no one could live up to that standard and thus everyone is considered a פרוץ.
However, Rav Waldenberg points out that most Rishonim did not accept this position of Rambam. Notable are the view of the Meiri, who opposes Rambam on the ground that it would invalidate everyone, and the view of Rashba, who writes that that rather than assume that everyone is a פרוץ, we should assume that everyone is fine unless known to be otherwise (and the statement of Rav in the Gemara should be seen as outlining simply a מדת חסידות). Rav Waldernberg further points out that Rambam may not in fact actually adopt the stringent view, as his statements elsewhere within הלכות איסורי ביאה seem to moderate that position.
In terms of who is considered to be a פרוץ for these matter, Rav Waldenberg rules that it is someone who is known to have violated issues of עריות in the past.
Rav Waldenberg concludes the teshuva with a discussion of whether or not having a child or the wife of one of the men present is sufficient to remove the yichud nature of the situation. He begins by noting that either condition is sufficient nowadays, regardless of whether or not the people are considered to be צנועים or פרוצים, on the logic that the presence of a child or a wife would prevent anything untoward from taking place. He proceeds from there to discuss several other details and contours of this aspect of the halacha.