[kizza42]

Keep in mind that your amp draw will drop slightly when in flight due to the prop unloading and you'll have airflow to keep things cooler. Depending on your self restraint, you could safely fly that 12x6 on 3S as long as you keep in the back of your mind to limit your full throttle flying. Its not like as soon as you go over the recommended amp draw the motor will pack it in. Generally it'll get hot to a point of the glue holding the magnets in losing its strength and letting go but its rarely ever an instant failure.
I used to fly a Hotliner with a Turnigy 3548 1100kv motor on 4s swinging a 13x8 prop! 1100Watts! But I always limited runs to 10 second bursts and it never let go in years of flying.

My other 3548 Powered plane was a Balsa Decathlon, I ended up running that on a 13x4 Prop on 3s, Was a hoot
https://www.youtube.com/watch?v=5WCiH6yqMx4