In my personal stuff I run a 298m Oberth because an after examining all the evidence I feel it supports the larger size; especially after seeing this pic. Note the standard docking port. I know the ship was intended to be smaller and not everyone will agree with my conclution but it's my personal stuff so
On how I came to the finall look for the mesh I went through this thought process.
1 This is based on a study model so that model lacks the polish if a finished studio model forcing me try and polish the design without straying to far from the base design.
2 I concluded for the pupose of this project that the ship would be entering sevice at a time in between Excelsior and Ambassador. To that end I have tried to make the ship seggest an evolutionary link between both Excelsior's and Ambassador's overall shapes. Also the study model's necelles are obvously on the design path for Obreth necelles.
3 The Constitution bridge modual and Oberth Necelles set the scale showing a ship around 330m long
4 Saucer and Necelle placement along with neck and pylon shape are evolutionaly between both designs. Saucer shape is experamentation with smother forward field propagation that leads ultimately to the Galaxy Class Saucer.