I have no experience with the method you describe. However I would strongly recommend in the future you either band them at birth or cut them at 4 to 6 weeks of age.  From my limited experience there is just no good way to castrate bull calves once they get past about 250 to 300 lb.

I have seen the Calicrate bander used on larger animals but even that requires a good deal  of time to drop and recover. I did change my mind on a bull at about 600 lb and my vet cut him at weaning. Much different than cutting at 250 lb but still probably my preferred method.  jmho.

Jim at Dawn