The principal adult and boy players in The Battle of Alcazar (which is the only early modern play for which both a plot and a printed text is extant) speak 98% of the lines, which is consistent with with the distribution of lines in extant prompt-books from pre-Restoration London that identify the names of the players in principal parts (27).
Of interest to me, in the plot of The Second Part of the Seven Deadly Sins, "four boys plays seven principal female roles" and while several of the adult principal roles are doubled "each actor who doubles in principle [sic] parts is off-stage for an interval of at least one full scene between roles" (29).
While the plot of The Battle of Alcazar is the only extant plot for which the text of the play itself is also extant, the plot is incomplete, and there is at least one instance where the plot differs from the printed play: a 35 line scene between Abdelmelec and Zareo is cut from the version of the play upon which the plot is based (31).
In assembling tables of parts, where one character is given multiple names, King separates them with a hyphen as opposed to giving the different character names their only row in the table (33). This is slightly different from my previous practice, but seems more logical. I'm only writing it down so I remember to implement it the next time I run into this situation.
Adult actors playing larger principal roles usually do not double, but lesser principals regularly double in one or two "minor roles" (33).
The book-keeper has added the note "Enter mr Goughe" in the left margin of one of the pages of The Second Maiden's Tragedy, which King says is "probably as a reminder that this new entrance for Memphonius should be added to the plot and that his new lines should be added to Goughe's part" (35). Again, while I agree with him, King's implication is that this is the only, or perhaps even the primary, reason for so doing, and all evidence I have seen suggests this is not the case.
In his edition of Sir John van Olden Barnavelt, Howard-Hill observes that there are too many "inconsistencies, obscurities, and errors," and that "the manuscript did not give a prompter all the information he would have required to guide performances" (35 - 38). King seems to accept this without comment, but the suggestion that a book would be used to guide performances would seem to imply that a prompt-book is used in guiding the performance.
The manuscript allowed-book of The Honest Man's Fortune was probably based on a prompt book, and contains a scene (5.3) not printed with the play in the Beaumont and Fletcher Folio (1647) (40).
Assigning the greatest proportion of lines to principal players allows them to rehearse their parts independent of supernumeraries for as long as possible (48). This makes a huge deal of sense in light of Stern's argument that most of the time an early modern player spent in rehearsal would have either been on their own with the part, or in the presence of an instructor.
Evidence of who played which roles in the early modern London playhouses suggest that a single male sharer in the company tended to play the largest roles in a given play, with the other principal roles being distributed largely among company members. Principal players might have doubled with smaller roles (roles with less than 25 speaking lines), and hired men taking on other non-principal roles, and perhaps (along with playhouse staff) filling supernumerary roles as necessary.