id say give it a go , ive a whippet well i think there might be a 1/8 greyhound in him(7 year old) but anyway a great dog on the rabbits and rats but was never intersted in tackleing a fox would of run them in the lamp but only ran alongside of them and that was it, well ive a bullx nearly 13mnths old and have taken 4 or 5 foxes with him but the point being that the whippet is now getting in on the action he would never be able to kill a fox but he now will have a go once the bullx has a hold of the fox so if you run both dogs theyd mayabe bring each other on
Frankieyou say your 13mt