No one painted themselves into a corner. ILM set it at 2397.75 when they scaled up the ship. That has become the official
length, size of windows and such notwithstanding.
The old "Enterprise Tour" website associated with the first movie had the specs:
-- Mass: 495,000 metric tonnes.
-- Length: 2500 feet (only 103 feet from 2397, maybe someone rounded up, but it's not 1200 feet, either).
-- Saucer diameter: 1100 feet.
-- Ship height: 625 feet (about 60 stories).
-- In a sentimental nod to reality, it said the ship's designer was W. Matthew Jefferies.
-- I believe the site also offered a tour of parts of the Enterprise not shown in the movie.