you had said
“since minhag does not trump halachah, held we should duchan.”
However the GRA then changed his mind and did not institute duchening. If he held it was halachicly required he would have. Which now that I think about it, arguably makes my case stronger. He held the reasons werent good or no longer applicable and nevertheless, did not re-institute Duchening.
A halcahic decesion doesnt get decided based on fires.