Enfold Accordion Slider Custom Image Size

Hi Kriesi
I would like to add a custom image size to the accordion slider.
So i tried the following from post
here
and added

add_filter( 'avf_modify_thumb_size', 'enfold_customization_modify_thumb_size', 10, 1 );
function enfold_customization_modify_thumb_size( $size ) {
	$size['aviaccordion-slide'] 	= array('width'=>345, 'height'=>321);
	return $size;	
}

but no change, how can i change the accordion image to a custom size?

Thanks a mill