New Moto Guzzi Door Mats Available Now
You could try a double o-ring outer body to see if that helps.https://www.mgcycle.com/index.php?main_page=product_info&cPath=193&products_id=4793&zenid=300d42ad816e231a69ade5e58b450bf3Ultimately though, the best way will be to bore the rear cover and sleeve it.