This happened at a local tournament and our judge couldn't give us answer.

I have Gigantes in atk mode on my field and my opponent has Grandmaster of the six sam in atk mode with one card face out in spell/trap zone.

He attacks my gigantes with grandmaster destroying it.

Gigantes effect activates and he trys to chain with his face out (cunning of the six sam).

because Cunning doesn't alture the atk/def of a monster in play, it can't be activated since Gigantes effects activates durring the damage step right?

If someone could clarify this for me that would be great. thank!

Correct, Cunning of the Six Samurai cannot be activated in the damage step, which is when Gigantes' effect resolves.

thats what I thought, thank you! that was the ruling that the judge made too, but I just wanted to be sure. Thanks again

Darn he beat me too it.
Curse's foiled agian x3.