You'll need to measure for yourself with the coach loaded for travel with your specific coach/tow bar and vehicle. There are many different models of blue ox tow bar, many different jeeps and base plates... not only that but your coach loaded for travel may not sit the same as the same coach loaded for travel by someone else.
Make sure to consult the tow bar manual as far as how level the tow bar needs to be, typically they'll specify within 'x' inches of level.