<?php it_exchange( 'product', 'featured-image', array( 'size' => 'large' ) ); ?>
<?php it_exchange( 'product', 'featured-image', array( 'size' => 'thumbnail' ) ); ?>
and I now have a thumbnail on the store page, and the large image on the product page.
There is, however, a WARNING in the .php file (yes, I ignored it) with instructions to copy the content to /exchange/content-store/elements/. This directory does not exist. If I follow the warning and make a copy of featured-image.php, where should I copy it to?