Snippet to add extra weight with every package of the UPS rate request. WooCommerce UPS Shipping Plugin: https://www.pluginhive.com/product/woocommerce-ups-shipping-plugin-with-print-label/

function.php

add_filter( 'wf_ups_rate_request', 'adjust_package_weight', 20, 2);
function adjust_package_weight( $rate_request_data, $package ){
    $package_extra_weight = 5;

    $req_arr = explode('<?xml version="1.0" ?>', $rate_request_data);

    $xml_obj = new SimpleXMLElement( $req_arr[2] );
    foreach ($xml_obj->Shipment->Package as $key => $package) {
        $package->PackageWeight->Weight += $package_extra_weight; 
    }

    $doc = new DOMDocument();
    $doc->formatOutput = TRUE;
    $doc->loadXML($xml_obj->asXML());
    $req_arr[2] = str_replace( '<?xml version="1.0"?>', '', $doc->saveXML() ) ;
    
    return implode('<?xml version="1.0" ?>', $req_arr);
}