Hi Andy mate.
Hope this helps- forgive the crappy drawing lol
The tow hitch isnt a problem IF the main part is removable. If not, it will completely ruin the 'exit' angle of the rear end by a considerable amount that usually means the exhaust ceases to become the issue, it is the towbar that becomes a problem.
Well, to put it more clearly, the tow BAR attached to the underbody is not an issue - it is the towing ATTACHMENT bar unitt hat is the issue unless fully removable for off road. (read up on exit angle for off road)
Look at this crappy picture of mine
As you may be able to see, the exit angle without the towbar hitch unit is MUCH greater than WITH the hitch unit
Hopefully you can see that the hitch bar would foul long before the exhaust.
Now, if you look at the diagram of my towbar assembly, you will see that the hitch bar and ball unit is removable below the bumper for offroad use. (mine has to be unbolted) - many more expensive ones can be removed quite easily
Here is the description of my unit. (attached)
Hope this all makes sense ? if not please ask
Cheers Andy
Joe