John T is correct...
D J Flyboy,
There are fundamentally two considerations with regard to this issue. First is CONTROL. The second is PERFORMANCE.
Vmc will decrease with altitude in a normally aspirated engine due to the fact that the engine is producing less thrust. Therefore, your control surfaces, at a given speed, will be better able to counteract the yaw tendancy due to a failed engine....when the remaining engine is producing less power. There will be less yaw into the failed engine, because the operating engine is producing less thrust.
Performance is related to the 5 degrees of bank issue. This has to do with sideslip, drag (DRAG is the key word....as, with an engine out, there is less thrust to overcome the drag. This is a performance issue, not a control issue.), and slipstream, fuselage drag, etc.
To address the comment about 300 feet AGL, stalling, etc., John T is correct: "Can you say 'SPIN'?
To explain: Usually, at lower altitudes, where the engines produce their best thrust (denser air, more air), the aircraft control is Vmc limited. That is to say, the aircraft will reach its Vmc and roll over on its back before the wings stall.
At higher altitudes, the Vmc is lower and will approach the stalling speed of the wings. At some point, with low power on the operating engine(s), the power output is little, and the wings will stall (You will reach the stall speed, as the plane decelerates, before you run out of aileron and rudder.)
So, when you do this training stuff, you either stall first, or roll first. All is well.
But, wait, there's more. What happens when the roll speed and the stall speed are the same? Can you say 'SPIN'?
And, this is what gets people in trouble. In any aircraft, stalling in uncoordinated flight will induce a spin.
So, you've lost weight; you started exercising, quit smoking, etc., and your life longevity is increases....maybe by many years.
But, when messing around with a multi-engine plane, hitting the Vmc and stall speed at the same time, your life longevity is now reduced to seconds. It's unlikely you'll recover. Especially with a C.G. that is aft of very forward.....
There are many sources of information that will explain this to the new, multi-engine student. Research, have a read, then you'll understand.
Fly safe,
PantLoad
P.S. Please don't do stalls or Vmc demonstartions at 300 feet. This is downright stupid.
(Edited to add the post script....)