At line numbers 23 to 25 in woocommerce/woocommerce-integration.php file, you can try deleting/commenting these lines –
add_filter('woocommerce_get_image_size_shop_catalog', 'mo_shop_catalog_image_size', 1);
add_filter('woocommerce_get_image_size_shop_single', 'mo_shop_single_image_size', 1);
add_filter('woocommerce_get_image_size_shop_thumbnail', 'mo_shop_thumbnail_image_size', 1);
and see if that helps enable the settings and then change the generated thumbnails. You will need to use Regenerate thumbnails plugin after you set new dimensions for the images (as per the settings page of woocommerce).