IMHO for a running dog a small dash of Bull should be plenty,lots of lurchers kill a lot of foxes and these dogs have no bull blood at all.The only time more than a 1/4 bull comes in handy is for working with terriers.I could forgive a Bullx missing foxes through lack of speed but one that misses through lack of bottle is only good for one thing a one way walk.1/4 Bull lurchers that lack bottle should not be bred from simple.JMO.