I'm not going to belabor too much about the ship's size, as most ships in Star Trek are quite inconsistent in this regard. However, I personally believe the ship is a bit larger than 120 meters.
I'm well aware of the discrepancies in size, as featured in TNG, but the vessel's creator Nilo Rodis designed it for a length of 120 meters because he also specified this size in his comparison chart (which then was authenticated by Andrew Probert).
Is there really a good reason to "believe" that in Kirk's era the vessel exceeded an overall length of 395 feet?
You do realize that there are other Oberths with names that have nothing to do with science?
Yes, like the multi-talent Peter and the video game programmer Christian whose contributions to mankind will have outranked the accomplishments of Hermann, one of the three founding fathers (next to Tsiolkovsky
and Goddard) of rocketry and astronautics, so Starfleet will name a class of vessels after Peter and Christian.
Sorry, I can't believe you are debating what is so obvious. You are certain you're not trying to find fault?