Modify the Order Weight for Table Rate Shipping Settings

betrs-modify-order-weight.php

/*
 * Adds additional weight to cover packaging costs.
 *
 * Requires Table Rate Shipping 4.2+
 */
function betrs_add_packaging_weight( $calculated_totals, $items ){
    // weight to add
    $add_weight = 350; // change this value to weight needed
    
    // add weight to calculated totals
    $calculated_totals['weight'] += $add_weight;
    
    return $calculated_totals;
}
add_filter( 'betrs_calculated_totals-per_order', 'betrs_add_packaging_weight', 10, 2 );