Old Smokey,
thanks very much for taking the time. I appreciated that the relationship was not linear; I was after someone who could explain a complex problem in simple terms, which is exactly what you have done. Thankyou very much!
In my world the Ford Laser has replaced EVERYTHING as the yardstick of equivalent power! (But only if it is off-blue, has two hubcaps and is rusty).
Cheers,
Mirv