Many hours ago, I replaced the factory knives with Redekop 650? knives. They are a grade above what was factory for our 2011 MAV.
At that time, I also put a bit larger wind blade on each end of the drum. They barely fit but are bigger than factory. I am not sure if they are necessary.
The best, but also final improvement I did was the stainless fins on the tailboard. Bigger in every direction and have a smoother, larger curve to the side. I did three on each outer side of the tailboard and left the inner fins alone.
I am not sure if all all of the above changes are necessary but IMO, the fins are needed for a good 40'.