I think it is quite often being forgotten that there are clearly defined modifications that constitute a new version. They either change logistical characteristics (E-1, E-3, E-4) or tactical ones (E-7). Obviously, such modifications like canopies, radio masts, wheels, etc. are not important and do not constitute a version.
In this particular case, the only modification that makes any difference is dropable fuel tank. I am not sure, what will be the version if such installation is removed.
