Excellent and useful post FFF.
From my place as a non instructor, but tester of such things, I will offer a few additional thoughts to FFF's, though not to contradict....
The Vmca number in the flight manual, which you are aiming for, you may actually find you can better, for two reasons:
If flying a normally aspirated twin at altitude, you started loosing power as you climbed, so you don't have as much asymmetrical power to overcome at altitude. So, you can fly more slowly with the rudder effectiveness you have up there.
The Vmca number is also predicated on a speed at which a sudden loss of power can be managed. You can manage a slower speed, if you creep down to it well prepared.
The weight and C of G of the aircraft may also affect Vmca, though not always as you would expect, so read the flight manual...