Your ferret does need a good big cage so it can exercise and keep it self fit as the cage that you put your ferret in will be its all world when it is not rabbitting
It will make it more tame if it does not have to pace up and down a 2ft or a 3ft cage it will have better health as well remember your ferret is like shot in a gun no mater how good your equipment is with out shot or your ferret you will kill nothing