I cant understand why you would want to change the setup you have if your happy with it. You do have to remember it is a defender you have, they tow well,do offroad really well but they are not racing cars or motorway cruisers. I guess you will have to make a compromise somewhere as others have said.
That's what I was asking really, racing car I know but that's not what I got it for but the motorway is a necessary evil. That's where the overdrive option found favour as it did not change the vehicle just gave me a 6th gear.