Sacrificing 3 Diplos with around 78k health each will give a perfect tame. Did this yesterday on a single player world and managed to get a 150 male Carcha (tamed 225), only issue is you've got to surround the carcha in metal gates and place a behemoth gate and door in between the Carcha and Diplo in order to prevent the Carcha from eating the Diplo without you mounting it