Guys, its quite easy in fact: The veritical fin is not the only thing, that prevents a plane from skid and shift sidewards. The whole hull itself does also. Some planes have a wider hull, some a tighter. How big the ammount of helping stabilizing is, is determind by the shape, the lenght and the area.
Never wondered why such planes like this could fly wonderfull even with such small fin (is there even any?):
Its the fuselage, that also helps.
It is different with planes with more power and, torgue and rounded fuselages, but still, the effect is existant.
And I can imagine, that a pilot can do wonders with increasing and decreasing the power of the outside engines, just to correct the orientation of his B-29.
It not a handy nor an simple flying, and its much dangerous, but I don't think, its impossible.