And so it is, and all who have not prejudiced eyes can see it in his model.

He, with his outer circle of chapels, in the first place takes all the light from the plan of Bramante; and not only this, but he has not provided any other means of lighting, and there are so many lurking places, both above and below, all dark, which would be very convenient for innumerable knaveries, a secure hiding-place for bandits, false coiners, and all sorts of ribaldry, and when it was shut up at night twenty-five men would be needed to clear the building of those in hiding there, and it would be difficult enough to find them.

There is yet another inconvenience: the circle of buildings with their adjuncts outside added to Bramante's plan would make it necessary to pull down to the ground the Capella Paolina, the offices of the Piombo and the Ruota, and more besides; nay, even the Sistine Chapel would, I believe, not escape." May it not have been that this malicious arrangement of Sangailo's to destroy Michael Angelo's masterpieces made the great artist so bitter against him.
Paul III.

conferred the post of architect-in-chief at St.Peter's upon Michael Angelo on January 1, 1547, "commissary, prefect, surveyor of the works, and architect, with full authority to change the model, form, and structure of the church at pleasure, and to dismiss and remove the workmen and foremen employed upon the same." For all this work Michael Angelo refused payment, declaring that he meant to labour, without recompense, for the love of God and the reverence he felt for the Prince of the Apostles.

Speaking broadly, the former architects had designed ground plans of St.Peter's on two lines, the Greek and the Latin crosses.
Bramante, and Baldassare Peruzzi used the Greek cross; Raphael, the Basilica form, the addition of a long nave made the plan like a Latin cross; and Sangallo, by adding a huge portico to Peruzzi's design, made his ground plan a Latin cross.