WooCommerce script to add weight of packaging to total cart

I would like a script for the functions.php file, or a stand alone plugin, that allows me to add the weight of the packaging (530g) to the total weight of the cart.

I have seen this script online but it doesn't seem to work:

// Filter to add packaging weight to total weight
add_filter( 'woocommerce_cart_contents_weight', 'prefix_filter_cart_contents_weight' );
function prefix_filter_cart_contents_weight( $weight ) {
/* Add 500 units to the total cart weight */
return $weight + 530;
}

Another similar script here is but I can't get this to work either:
https://stackoverflow.com/questions/64416812/filter-woocommerce-cart-contents-weight-not-applied-for-shipping-weight

Many Thanks

Chris