Yes, that's right. You'll always be able to have a minimum of 5m/sec acceleration upward as long as you're using the rear or bottom thrusters to do it. The thrusters take time to ramp up to this cheaty-level of thrust though, so it's very hard to stop a fall in a high gravity environment. Once you're past about 3G of gravity, it's all pretty much the same, since all thrusters will be underpowered and rely completely on the flight assist cheating.
What's amusing is that when you engineer the thrusters, the permitted mass can drop to a level that the thrusters aren't allowed on the ship anymore. It won't force you to remove them, and you can still fly. However if you remove them, you won't be able to put them back on, and it may also prevent you from switching out other modules, since your ship will be overweight. The UI isn't very clear about this, and it gets very confusing.
What's amusing is that when you engineer the thrusters, the permitted mass can drop to a level that the thrusters aren't allowed on the ship anymore. It won't force you to remove them, and you can still fly. However if you remove them, you won't be able to put them back on, and it may also prevent you from switching out other modules, since your ship will be overweight. The UI isn't very clear about this, and it gets very confusing.