Typically what we do is always leave the PID output as 0-100%. We read the minimum and maximum output parameters from the VSD and then scale to that before sending the command on to the VSD (in the case where your VSD doesn't do that already.)
Don't be too hard on him. Australia also bought into that crazy fad called the "metric system" we heard so much about back in the 70's and 80's. I'm sure in time they will catch up with the modern world.