5milesbaby,
That makes sense completely.
I think the reason we were cancelling and refiling was for that very purpose, as by the time we had run the CFP ( computer generated flightplan ) to ascertain levels and speed, it was just as easy to file it direct from there as to type out a seperate CHG message. It also alleviates the margin for error with the CHG.
One related question : if we send a CHG for type / level and speed only ( ie not a route change ) and a slot has already been issued - will we be classed a 'late updaters' ( ie 'LU' in RCA ) and penalised accordingly ?