Have a look at your front door roof ledge you will see a plastic bung, this is the locating hole for the front roof bar.
If you look very closely at your rear window glass, on the upper edge you will see two arrows pointing up like this ^ ^ about 3inches apart. 3door definitely have this but if you have a 5door it may have another locating hole like the front but I doubt that as I'm led to believe 3dr and 5dr bars are interchangeable.
Measuring from the front locating pin point to the middle of the two marked arrows will give you a rough idea of the gap. I would nip out with a tape measure as my bars are on my car for my board mount but I'm 3000miles away from it with work at the moment, sorry!