I am often puzzled by those who think the K4 is an "easy-mode" plane. There aren't many, granted, but they seem fairly vocal.
How many times have you seen new players ask the arena something to the effect of "What is a good starter plane?"
In all my time here, I've never seen any 109 recommended on Channel 200; let alone the K4. In fact, for an even mediocre player, I'd contend that the plane is more a danger to the driver than anyone else.
The plane is one big "if."
"If" you can hit with it, the 30mm will kill most aircraft in one shot.
"If" you can force a fight to the vertical, you have the advantage.
"If" you mind your speed in a dive, you wont lawn dart.
"If" you are gentle with the throttle, you wont snap spin and auger.
"If" you can learn how to manage the engine torque, it becomes an asset.
"If" you can't do any one of the above, you're not going to last very long.
It is by no means impossible to fly but I think the list of quirks present make it anything but an easy-mode plane. Should one have that opinion, I'd gather it's fair bet you're simply running into someone who has a pretty good idea of how to wrangle the best performance out of the aircraft.
If it were such an easy plane to use; the arena would be filled with K4's instead of Spitfires.