I do know that to trim out an outboard engine failure, one never needs more than 4 divisions of rudder trim to hold it nicely (about 1/3 available on the indicator). Two engines out on one side can require full trim and a little bank to balance it out, but losing two on one side instantaneously is almost unheard of- even with things wrong, jets still produce power. Therefore more than adequate rudder authority is designed in by far more knowledgable people than I. Boeing produce good aircraft and I'm happy to accept their stamp of approval! Sometimes certain take-offs approach the limit (as in Min V1s), but still no problem if willing to take a turn instead of climbing straight ahead, and the danger patch is of very short duration.