The tank bag on the used GT I bought several years ago is shot. The zipper is messed up and the clear top is brown ,cracked and falling apart. Yesterday I met someone who mentioned he had a new RT tank Because of different mounting points on the front of the bags he doesn't think it will work on the GT. Both bags are from BMW accessories and look very similar.Both bags have a single front strap and two in the back. Does anyone know if the bags are interchangeable ?