prob not so much size of the dog dave, more if its got the balls=heart for the job , but suppose bit of size would help though with them big buggers lol, same with fox dogs once they been nipped few times, some think twice , that's when heart for the job comes in, funny thing a lot of dogs will tackle most deer but not foxes lol, strange creatures are dogs mate.
no point in keeping a dog that can't take the bushy manI think most dogs that don't do fox but deer are just scared of the teeth ! And personally if wont retrieve a shot fox wouldn't be in my kennel !