Seems I had a bit of a brain fart as I needed to enable the brake chopper function which was in the extended parameters. They weren't that easy to get to as they're normally hidden and a code has to be entered to access them but she's now stopping about 1.1/2 turns of the chuck, which is quite good considering the amount of iron being moved at speed and I don't have to rethink my carriage control system now either so it's all good