The post production house that develops your film and makes you a digital work print will probably give you a tape where every fourth frame is doubled. This will make 24 frames equal 30: 01-02-03-04-04-05-06-07-08-08 etc. If you recorded double system sound it shouldn't cause any problems. As one second of film still equals one second of video. But you mention optical track. Did you record your sound directly to your film? If this is the case, then you should ask your post house and not us.