After seeing a photo of an Enterprise-A model kit decal of the airlock port, I will admit that it definitely looks like that's what it is. However... I still don't believe that the Oberth class is 120 meters, and I don't particularly care what someone wrote on a sketch. I think it was always larger than that; ergo, it is the same size in TNG that it was in STIII. And this docking port decal actually shows that. Those ships are all at different points in space and at different positions relative to the camera. How do you determine each ships' relative size to the other? Since not a single one of your reasons can be backed up by canon proof (other than a small registry number which also cannot be reliably used to determine a starship's age), I will certainly continue to believe what I believe.