I do believe it is possible that the underboss could maintain a regime and I can certainly think of a few cases where that was true (e.g., Marco Reginelli and Philip Leonetti from the Philadelphia family, possibly also acting Philadelphia underboss Frank Martines). In fact, I also believe that it did happen with the Colombo family in the 1960s but, as the evidence suggests, with Mineo, not Franzese.

The fact that Franzese had an acting capo does not prove that he was the underboss (as there are several other explanations, such as law enforcement heat, to explain why acting capos are promoted), nor does it disprove that Mineo was the underboss. Mineo was repeatedly documented to be the underboss and served in the role while simultaneously having his own regime (until Persico was given control of it). Franzese having a level of respect and influence greater than most captains does not make him the underboss.

I have read your biography of Franzese and was disappointed to find no actual evidence or sources to support your claims that Franzese was underboss in the 1960s or that he was promoted to capo in the 1950s (whereas Scarpa clearly states that Franzese was promoted by to capo by Joseph Magliocco in 1962). If you could provide me with any links to documents, files or reports to substantiate your claims I would happily take that into account and weigh it against the, as I see it, compelling and consistent identification of Charles Mineo as Colombo's underboss.