As the JCB team have enough track time and they are planning 'low speed' airfield testing in the UK, they should be able to get up to speed - but probably not during the first seven days of speedweek.
After all in 1999, the UK Richard Brown bike team got to 326mph after just six runs on the salt and 330 mph on the seventh pass. And this team had come from the UK with a National record at just 216mph.
It will be interesting to see how the JCB team get together on the salt to achieve Andy Green's target.