If the aircraft only decellerated from 148kts to 79kts in the 5000ft available (69kts speed loss = 13.8kts per 1000ft) then surely it would have still overran if it had landed 3000ft earlier at the correct point?
Nope. Don't forget your basic physics - Kinetic Energy is a square law.
Touch Down 148 Kts.
Overrun at 79 kts.
Back of a fag packet type calculation, assuming contstant braking rate (a big assumption, but good enough for now...)
79^2 / 148^2 = .284
i.e. the a/c had 0.284 of its Kinetic Energy left, or had got rid of .716 of it in 5,000 feet.
5000 / .716 = about 7,000 feet, so it needed about 2,000 feet more.
CPB